Or opponent is feeling mercy for myself and thinking... This guy won, let him go away happy... or he may think "He lost, but I don't want to beat him again...
Why does no one accept my rematch?

I never said they were under obligation.
You just called them "cowards" for doing the most natural thing in the world (playing another chess game against another player).
Yes I did. And thats what they are. The most natural thing for a warrior to do is go head to head with his opponent to see who is stronger. The natural thing for a coward to do is run. But again I never said anyone is obligated to rematch.

To go head to head and see who is stronger? Funnily enough when these people lose they are keen to play the same person again lol.

Lol.Perhaps feel as Challenge.Insistence.But that's can work emotionally not so Good I opine.Perhaps is best idea to add to friend and wait other moment and prep again.In other way, emotion of moment can be used as energy to try the victory.Not my case.So far of feel bad or frustration,if rival deserve victory is good to me.
People here are insecure and really hate to lose, since in chess is a 1v1 and you cant blame teamates for mistakes, so they rather win once and run rather than let the opponent try once or twice with other tactics

Because there are tens of millions of players on this site. I would rather play against someone else.

I never said they were under obligation.
You just called them "cowards" for doing the most natural thing in the world (playing another chess game against another player).
Yes I did. And thats what they are. The most natural thing for a warrior to do is go head to head with his opponent to see who is stronger. The natural thing for a coward to do is run. But again I never said anyone is obligated to rematch.
but they just went head to head and beat the other warrior or whatever. How many times do they have to go head to head with the other warrior before it's been determined that they are a true warrior?
Agree that we are making imagination exercises.I use the term "perhaps".Also is posible that he won the lottery or something and go to celebrate.Or the tea or cafe falls,or the rival remember that is on tv their fav serie or music show.Can be a clasical.Oscar winner or comedy.Thats happens just on the moment when you send remacth petition...