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.