another reason is that they may be afraid that you are going to be the one running if they lose their next game.
1 game chess coward phenomenon

Because thier online rankings matter to them. Losing to the same player over and over drops thier score, even if the two players are somewhat evenly matched. Winning against an evenly scored player even if the player seems evenly matched won't increase your online score enough to change your ranking. If the games are mixed bag, say 3-2 in a five game match, both players scores will go down.

On the phone, the new game button is on the right and the rematch button is on the left - this makes the new game button slightly more convenient to hit for right handers based on thumb position. (I happen to be a software UX expert and can appreciate the impact moving a button can make on click-through.)
Chess.com should consider swapping the buttons to get a larger rematch ratio for right handed cell phone players.
fair reason,that's why i regret having rejected rematch offer from an opponent that i beat i message him to say appology and ask him if he wants a rematch but he doesn't reply, i guess he might say rude things in the message that i didn't read if not so then why he doesn't respond to my message

To each his own. I personally accept rematch 90% of the time unless I have to go, and I only offer rematch usually when we chatted during the game or when the game was really fun.
What *is* cowardly, is when my dad (works from home currently) takes a break from work, plays one game where I easily crush him in 20 moves, then makes excuses about getting back to work and 10 minutes later I find him playing crossword puzzles on his phone.
I once played a bum in Berkeley and he kicked my ass all over the board. I asked him for a rematch and the guy's reply was epic, "if I'm gonna smoke you another time I want some of your friends watching". I laughed and bought the guy a pizza slice and coke.
Dude, get over it.