People start wanting to have guesses to have a raw idea. But along the way, the guestimate becomes a pseudo « promise » and people end up asking why things did not go as « guestimated ».
Also, when you are asked to guestimate, the asking person generally already has an intuition. In that case:
- either you provide a number close enough to the one of the asking person -> everything is ok
- or you provide a number much lower or much larger -> you are asked to justify the guess. This makes no sense, as system 1 does not give justifications.
In the end, it becomes more of a game of guessing what the other person has in mind rather than being sincere.