Personally, I need to practice leetcode style questions pretty regularly in order to perform reliably without reference materials. If more than a couple of months go by, the details of particular algorithms begin to fade.

I think it's unreasonable to expect people to spend their off time practicing these sorts of problems, in the same way we think it's unreasonable to require everyone interviewing to be working on personal development projects over the weekend. I suspect most working people simply do not have the time.