You mean the breakaways, or you mean the guys who try to go out with 1-2km to go?
With a breakaway, there's always that chance you can ride away with a win, which is enough for most people to try it if they're feeling good (and usually not up in the overall classification). With attacks really late...well, sometimes you can lead your teammates out enough, sometimes you can't.
Saw Farrar take Stage 3 on Monday, that was a pretty hectic finish for everyone. I hear today was a lot cleaner with Cavendish throwing down.