Perhaps I’m biased as someone with a better than average sense of algorithms and discrete math, but I think such interview questions have a lot of utility, provided the job will require some analysis of algorithms, eg you’re working on the platform, or a solver/optimizer.

Obviously it’s pants on head stupid to do that if you want a web dev to make a pretty app, tie frameworks together and liaise with 3rd party integrators. However, I think many employers want the crème of such devs who are also good at algos.