Knowing the same interview questions doesn't make you competent. That's the problem. By asking questions not related to the work you filter out people who do the work you need, and only accept those who spend time passing interviews. Same as how ACT's filter for test takers, not ability to learn nor domain knowledge.

The core problem is these interview questions are asked without knowledge as to why they're doing it. "It's industry standard" isn't a reason, but it's why binary search tree questions still exist. Some people understand that they're filter questions, but overwhelmingly interviewers think they're real problems related to the job.