When I first joined a site like this I started a game.
I made a move and waited... hmm, my opponent was taking a long time. I look up at the clock and it says 3 days? WTH?
I logged out and never went back.
Which is to say I think some new people think it's live. When they realize it could last weeks or months they abandon it.
Also there's a good chance zero of those people will read this topic...
I've had three games in a row against unrated players, be abandoned. In the seven months I've been on chess.com, a majority of unrated game challenges I've accepted, have been abandoned giving me a "win" on time. I don't mind a win achieved through play or resignation, but for someone to abandon a game after the first or second move and run out the 3 day clock is unforgivable. I won't play any more unrated games.