Understanding the limitations of libraries might help you use those libraries better. Using libraries can be a part of delivering business objectives.

I don't think that list reversal is a good interview question. At least not as a positive discriminator. Though it might help you weed out people: I'd probably not want to hire people who can't figure out how to reverse a list. If they'll stumble upon such a simple problem, they might also stumble over the more complicated problems we have to solve to deliver business objectives.

I wrote `can't figure out' deliberately. Not knowing how to reverse a linked list, but being able to come up with an algorithm after a few minutes thought is perfectly adequate.

I agree with you - it is a weeder-outer, but not an includer-inner - there are lots of people who can write code to reverse linked-lists that I don't want to hire.

In particular I don't want to hire the people who would rather write their own implementation than use a library (think Not-Invented-Here and Yak Shaving).

Indeed. By the way, in purely functional implementations of a list reversal there are non-trivial trade-offs to make. (See Janestreet's standard libraries for OCaml.)