For some strange reason, a lot of people seem to think that Poker is very easy, or at least that it is a game purely of luck. By those rules, people will act in a very strange fashion, completely at odds
with probability (ho ho). Televised poker and the general explosion in poker facilitated by the internet has meant that any muppet with a bank account (oh, that would be everyone, then) can just sign up and be playing within minutes. For the average working joe, a dollar or even 10 dollars is more or less nothing so this increases their willingness to just throw it away chasing some miracle or other.
Another possible reason is that a lot of people dont want to risk being outplayed on the flop by players they know are probably better than them. Hence, all-in preflop. They dont really think about other peoples hands, only their own, and the thinking is "Well, my two cards seem quite good, I'll just remove any need to be clever or tactical come the flop by throwing all my chips in now".
It's a cyclical process too, because many poor players see this kind of thing happening all the time and witness completely donkeys doubling up again and again beating far better starting hands, so they think "Well why not?" What they dont see of course, is those players quickly losing their chips again later in the tournament when the stronger games win through.
For the record, in my experience, the standard of play is no better at $5 or $10 games really, especially those with the rebuy safety-net, and I've even played some $20 games where the play has been unbelievably poor. If you think you are pretty decent at poker and your BR can handle it, maybe $50+ tourneys are the way forward?