Guess culture acknowledges that there is a social cost to outright denying a request. A good example from Yvain's comment:

Consider an "ask culture" where employees consider themselves totally allowed to say "no" without repercussions. The boss would prefer people work unpaid overtime so ey gets more work done without having to pay anything, so ey asks everyone. Most people say no, because they hate unpaid overtime. The only people who agree will be those who really love the company or their job - they end up looking really good. More and more workers realize the value of lying and agreeing to work unpaid overtime so the boss thinks they really love the company. Eventually, the few workers who continue refusing look really bad, like they're the only ones who aren't team players, and they grudgingly accept.

Only now the boss notices that the employees hate their jobs and hate the boss. The boss decides to only ask employees if they will work unpaid overtime when it's absolutely necessary. The ask culture has become a guess culture.