Well, "a lot of software engineering roles" have requirements and knowledge expectations that are far out of line with what the job actually requires. There are some "fundamental algorithms, including things like DFS and Dijkstra's" that simply aren't applicable to a lot of software engineering roles, big and small.

Most of the questions and interview ceremony around these things, especially for the aforementioned positions for which they're largely irrelevant, are exercises in hazing, ego building/busting (depending on which side of the interview you're on), and petty power plays.