* I always have access to a decent stdlib and would not need to implement sort itself
* But I do need to design and implement bespoke algorithms
The algorithms are nothing groundbreaking - they're things like how to grow and shrink a buffer when reading from a socket. But I'd struggle if I didn't know a few examples of different algorithms and how to think about their trade offs, and basic sorting algorithms (not like this article!) are ideal for that. Maybe I'm doing unusual work but it doesn't really feel like it.
Edit: To put it another way: in a past job, we had some unfortunate examples of people being hired whose ability to work with algorithms was sadly not up to scratch, and it had a serious practical impact on their ability to do their job. If they had been asked a few questions about sorting algorithms in their interview then that could have been avoided.