Sometimes who offers rematch is slow to send request and opponent already began another game or he went online (off live).
Play once and refuse rematch

It's funny how all those guys mention that they were black, it doesn't matter when you hang pieces every single move!

There are tens of thousands of people playing on chess.com at any time as I understand it. Why fuss over someone not wanting to play two games against you back to back?

You lagged 30 seconds on the clock and been down huge on material, how was it close game?
It is consider polite to at least "gg" after being outplayed, and if you feel like you have a shot at someone, you can always send message with challenge. Just don't turn into a stalker or something.

How many times do you play with black, perhaps lose a close fought game... and then the opponent declines a rematch? It seems to happen a LOT with me. I always accept a rematch challenge if I have won (or lost). Am I alone in thinking that it is poor etiquette? Sometimes people have to go and do something , obviously, but would it cost a lot to type GTG?
Nobody owes you a rematch. They don't need a specific reason, to refuse another game.
And looking for courtesy on the internet is like looking for a needle in a haystack.

@2Q1C why is it "pathetic"? And is it pride stopping you from getting beating twice from the same player???

So WCC shall be decided by one game only, well all chess tourneys should go for KO format by your means?
With only Spanish game allowed....
About duels, if you got hit and unable to fire, your second was allowed to take a shot instead, also in case of miss, you often have been allowed to call off duel on honourable term set beforehand (contribution, apologies, etc).

If you fire first in a duel and miss, do you think I am going to let you reload and try again? No I am putting you 6 feet under and walking away!
Google: deloping

Idk, I am seeing rematch as a friendly gesture, rarely refuse them without outside reason. Also really like if someone allows me to have another chance. In the sense it is very educational, since playing the same person several times gives extra perspective. But my thinking can be extraordinary since I care very little for outcome of the game, usually.

If I get beat by someone I say gg. I dont ask for a rematch because you are basically saying the original outcome isnt right. It's like saying to your opponent after a game , "oh, err, I wasnt paying attention that game, thats why i lost" It's just rude.
If you fire first in a duel and miss, do you think I am going to let you reload and try again? No I am putting you 6 feet under and walking away!
I agree! Bring back the duel! If you politely request a rematch and your opponent "slaps you in the face" with a denial, you should have the right to avenge your honor with a duel! Awesome!

I often already have a new game by the time I get offered a rematch. It feels bad but I have to decline.

How many times do you play with black, perhaps lose a close fought game... and then the opponent declines a rematch? It seems to happen a LOT with me. I always accept a rematch challenge if I have won (or lost). Am I alone in thinking that it is poor etiquette? Sometimes people have to go and do something , obviously, but would it cost a lot to type GTG?
Please see the other 960,743,564,210,473,478,500 posts on rematches.
https://www.chess.com/forum/search?keyword=rematch
Sometimes people have to go and do something , obviously, but would it cost a lot to type GTG?
You don't type anything, do you? For example you could type: "Thanks for a game, would you like to play another one?" But no, you just hit the Rematch button. Why should I type anything? I just hit Decline.

It's totally the choice of the player if they want to play a rematch or not. There is nothing to be offended about.
How many times do you play with black, perhaps lose a close fought game... and then the opponent declines a rematch? It seems to happen a LOT with me. I always accept a rematch challenge if I have won (or lost). Am I alone in thinking that it is poor etiquette? Sometimes people have to go and do something , obviously, but would it cost a lot to type GTG?