Why do some players immediately resign the moment they lose the momentum? Is it ego? Pride? Shame?

     Some players' only enjoyment in chess comes from attacking. They will resign rather than play out an even game where positional factors and endgame technique will be important. They have no patience, and only care for the "thrill of the chase". I've seen several such players admit to this in similar forums. Some go so far as to resign as soon as they see it's going to be a closed game or positional struggle. These players will usually push for all-out attacks and once that has failed simply are no longer interested in that game.

     Completely missed the point. They would rather make an unsound sacrifice that gives them an inferior position but some attacking chances rather than have a winning position that they would have to grind out. They are perfectly aware of whether or not their position is good or bad or even and they don't care. Once they can no longer push an attack they lose interest and quit. This strategy works out well for them--they lose enough games that they could have won that their rating stays down and they can face weaker players who are more likely to fall into opening traps or fail to see impending mating combinations.

I'm in that range too and I believe they just don't have the initiative / energy to fight back. They want an easy win and aren't willing to work for the hard one and risk all that effort with no guarantee. Not a winner's mindset.

I have limited time and play for fun. 

I will work for a hard earned win when I have plenty of time.

Basically, the amount of time lost in that game could be used for another game entirely. 

If the other player is looking for a good game, I'm sorry, but I play for fun, and have no way of knowing if they are looking for a good game or just playing for fun.

I just resign because I'm not having fun or just not feeling it. The days where I'm dropping pawns and pieces randomly in lines i know tell me to just get off of cc and do something else, like play dnd or hearthstone.

     Still clueless, bud. Look at the original question. It's WHY do some players do this, not is it a good idea, or is it "sporting", or is it fair to their opponents. Quite a few players in similar forums in the past have admitted to resigning to start a new game anytime they get into a "dull" position, or put on a defensive footing, or no longer have good attacking chances. One person (NikkiLikeChikki, miss her comments) started a thread asking whether other players were being cheated because she resigned anytime an opponent played an uninteresting opening.

     I didn't say I think this is a good way to play. Obviously a lot of players will be ticked off to have their time wasted, or to be deprived of the chance to play out the game once they have thwarted the attack and gained some advantage. Nor are they deliberately sandbagging just to face weaker opposition--if they can't play defense worth a d**n they'll lose most of those games anyway.

     These players have just one thing they enjoy in blitz games, an all-out attack. As soon as that is unavailable they bail.

People play chess for different reasons.

Some players are dedicated to improvement. Other players don't care about improvement at all ("Why study chess? Takes the fun out of it!")

Some players take their chess games seriously, and stare, wide-eyed, at the board, while the gears in their head are churning furiously.

Other players don't take their games seriously, and are often surfing the web, in other browser tabs, at the same time. Sometimes they even forget that they're playing chess, and say, "Ah, crap. I forgot I was in a game," when their flag falls. <-- These kinds of players are actually quite common - and to them, stuff like "resigning" isn't really a big deal at all.

it depends on my mood. a couple days ago i made an opponent mate me with 3 queens against my lone king. why he needed 3 eludes me. i like mating with the tools i started with if possible.

sometimes though, a bad turn can just throw you into "i'm so not feeling this" frustration. i think a lot of it is being mad at myself for blundering and not wanting to feel like the elephant man (gambit?) drooling all over the chess board. sometimes my mind goes blank too when all my plans come crashing down... especially against trench weasels i'd abort every game against if i could. there's that too... why continue in a line you hate to begin with?

i quit playing a decade ago because i couldn't take any more stonewalling or scandinavian advance. (why isn't 2...e5 called the advance in the scandinavian?!!!)

Well you must have a seen a lot more than I have when you’re almost at 3,900 rapid games since January 2022; that’s a remarkable statistic.

I wouldn’t assume it’s their bruised ego.

It’s within character of me to counter attack and even sacrifice a minor piece or rook and come up empty. Oh well, my tactical visualization and calculation did not pan out.

It's good sportsmanship and none of the things you mentioned 

     Are New York City schools really that bad at teaching reading? Perhaps you were home schooled. The OP clearly describes the folks in question as having lost the initiative and being down material, a knight or bishop. If your chess lessons describe that as "winning" you need new teachers.

     I'm only telling you what other players have said on similar forums. I know you think you have unparalleled psychic powers that let you know what people you've never met really mean, but I take them at their word.

It often happens to me when I feel something cheap or ridiculous made me blunder a position that is otherwise "hard to fk up, really"... Like you play the only move that loses, with no apparent reason... It's hard not to resign after that because you are aware of post-blunder tilt...

In this game (15+10) my opponent was playing honestly amazing. Later with the engine yeah he gave chances that I missed, but during the game it just seemed he was playing really great moves throughout, and also I was taking time and he was playing instantly... We reached a tough position for me where I had 2 minutes and he had like 11, then he just tries to trick me in to the most obvious silly tactic ever and blunders a full knight... His resignation was completely obvious because he just played like a 2000 throughout the game and then blundered like a 850...

This happens to me alot too and in various stages of the game... 

What sheep is on heroin?

Excuse me, while I kiss the sky….

     Attacking chances evaporated, initiative blunted, down a piece and you call that a winning position. Perhaps you'd care to play a few high-stakes starting with those "advantages". Do you ever hear the GM commentators you so often quote say "Hiraku's attack has failed, he's lost the initiative, and he's down a piece. Surely he now has the win in hand."? Get real.

I have no idea what your talking about man my name is Hero in Sheep

as in... The sheep who is a hero deep inside, of course...

heheh

Lol different times.

Dude stop glorifying Heroin that's not cool... or chic  

Alright, I down graded from rock and roll, being cool to chess.

Fair enough.

Why not both?

David Bowie and Catherine Deneuve.

Sandbagging.