There may be a genuine reason for the abandonment, such as a poor internet connection.
However, in most scenarios I think it is an ego think - a player with a fragile ego may feel better disconnecting, or letting the time run out, rather than losing to a checkmate or resigning. Sad, really, but I don't think you can do anything about it. Just accept the win (and the points), smile at their insecurity, and move on to the next game 
Thanks for replies
When internet is lost there is a clear message appearing in the game that says opponent 'disconnected' adding player must reconnect within... 30sec or was it 60sec? don't remember, or the game will end and a winner declared. So there is a distinction between internet lost and game simply being abandoned. Accidental closing the tab/app is plausible but begs the question why so many are so clumsy.
How do they abandon the game? is there an exit button to push or do they need to do a log-out thing or closing of the chess tab? seem tedious to reload or re-login if that is the case.
Anyway, if game abandonment does not cause any diminished win/lose points or have any other impact than the game just stops with an instant winner, then so be it, it won't matter much. Just got to start a new game and move on :-)
(ps, giving up too early removes the possibility to turn around the game, people do make mistakes and you can win back pieces or even force a draw if lucky... why give up that I wonder?)
A newbie question. Relatively often when in a winning position the opponent suddenly abandon the game, the game stops and winner declared by 'game abandoned' with the winning points and these things. Actually, I hardly see people Resign, just game Abandon instead. I mean when a silly queen blunder happen and the opponent looses the queen or a pawn get promoted to a queen during end game or some development that make the game a loosing one for the opponent people just abandon the game. Some happily keep on fighting until the checkmate or battle until time run out which I like, feels better to loose or win that way.
I wonder why games are being abandoned instead of player resigning? Are there any practical difference or statistic/merit difference for either players when it comes to winning or loosing via abandon vs resign? You get credited with the win and can immediately start a new game so in that sense it seem like no difference at all except maybe poor sportsmanship?