It is also a signal -- "Can this person be persuaded to work for magic-big-number options but half the salary without too many question? If yes, then he's a believer and want him to work for us. He'll probably stay up on weekends and work for the cause." If he's asking too many questions, he'll probably question our decision making down the road as well, and will be hard to fool.

This can be seen in recruiting stagee as well, it is usually presented as the take home question. Give them a take home interview problem that takes two days to solve. Those that go for it, will be dedicated and desperate enough to be good workers.