Rage quit

Second game against this guy. First one, he makes some comment like "You missed mate" within a couple of moves. Not sure what it meant but disregarded. He went on to win. 
In the rematch, at the start of the middlegame, I set up a discovered attack. 
I immediately see 'reconnecting' next to his name, suggesting he has disconnected. When he does reconnect, he quits.

I then see a note under his profile from somebody else saying 'Please resign rather than leaving time to run down', suggesting that rage quitting is something this player does.

Why do some people have trouble just enjoying a game and accepting that sometimes means losing? 

Taken.. ✔

 NEEEEEEEXT ........

I think the chess.com interface sometimes doesn't recognize when someone resigns and then quickly closes their browser window.