I agree with you, but I have heard the opposite from some people. They like being able to memorize programming interview books and grind problems on LeetCode/HackerRank instead of having a portfolio or other alternatives.
From my time at /r/cscareerquestions, LeetCode is the "hardest" and thus the best for top companies. HackerRank is good but every challenge requires parsing STDIN instead of just giving arguments to a function the user writes. It's very annoying to me and a deal breaker, especially with certain languages.