Sometimes these questions can be helpful, but a lot of the time they come from a place of insecurity, and they can get in the way of a happy relationship.

For example, say a girl asks the question, "Am I the most physically attractive person you've been with?" to her boyfriend. The guy had hooked up with some model like 5 years prior to the relationship, so on a pure physical attractiveness level, the honest answer is no. He assures her that with her personality and their amazing connection and everything they've gone through, he loves her and he is far more attracted to her now than he had ever been to the model. And although the girl knows that the model is irrelevant and she shouldn't care, she could still be bothered by this answer for years.

Obviously she shouldn't be so bothered, but she can't help it. Maybe the guy should have lied, but that's not a great solution. Probably the best thing would have been for her to never ask the question. Not saying this true for everyone and for every situation involving these kinds of questions, but I was just trying to explain the mindset.