Never once has knowing about the performance of linked lists or hashmaps been necessary to fix an API issue. 99% of your API issues will be "this doesn't work for X reason", not "this API response is slow because weren't using X instead of Y data structure".
You sound like you've worked with significantly different code than I have. Your "never once" is my "almost always", and my "X reason" is often because I'm working with an immature, unreleased library developed by another team at my employer.
What's more likely: that everyone needs to know intimate details about basic data structures or that the world is held together with duct tape and Perl and 95% of code is written by people not in Silicon Valley who need it to just work?
