How do you not understand that many people with families or other external obligations wouldn’t have the luxury of spending 7 hours a week for multiple months on leetcode?
Like everything else, it's an opportunity cost. Personally, I think LC is a great return on time invested. It takes far less time and money than say, any of the traditional gatekeepers, even for example a CS degree, or even perhaps a good data structures and algorithms class that is semester long.
If they need to spend that level of time in order to do a few search or sort problems on a whiteboard I'd be concerned that they don't actually know algorithms or datastructures.
The kinds of questions most companies ask are not hard.