I don't know what your experience is, but given what other folks have shared here, it seems that those with 10+ years of experience in the industry, doing mostly "API programming," have said "I don't use this sort of knowledge day-to-day." I have nearly fifteen years in the industry. I am also entirely self-taught, and have never done any in-depth study on algorithms and data structures. There have been a few times that my lack of knowledge was limiting (and most of those times involved complex queries), but those times are few and far between.

But, you are correct: "a small edge can make a difference sometimes." To some employers that matters. To others? Maybe not so much. Maybe they are happy with a few folks that can deal with the algorithm issues, while the rest of team cranks out APIs and fixes bugs and supports old products.