The objective of asking these leetcode style questions is to find candidates who are willing to put in the time to study. Success signals that this person is willing to commit to performing well at something that is reasonably challenging. The end result is that they are trying to hire worker bees. This makes sense as the bulk of work at any large company is largely mundane and relatively routine. I'm willing to bet that when a company wants to hire a two sigma candidate they don't go through all this nonsense, although at that point the candidate is already well known in the industry most likely.