Partly it's because when stuff's new, it's exciting. If we went back to a few years ago, I'm sure we'd see all that stuff and think it was boring, because then everything was fresh and new, even when it was fresh and new and bad.
All these things go through phases. Look at the world of movies, where there're often a few slow years and then a few bursting years. But the world of startups is much newer and much younger, and so we haven't gotten used to these cycles yet.
That's true, although recently I've been hearing a number of so called important people saying that the whole computer/internet thing is done and is settling down to incremental innovation at about the pace of the rest of the economy from here on in.
Now of course the answer is that no one really knows what's coming but recently I have started taking that point of view slightly more seriously and have stopped taking the next big web cycle as such a given.
All these things go through phases. Look at the world of movies, where there're often a few slow years and then a few bursting years. But the world of startups is much newer and much younger, and so we haven't gotten used to these cycles yet.