Just because you're not writing high performance software doesn't mean it shouldn't be a consideration. Sure, I'm not gonna micro-optimize memory when I'm writing an API in Python, but that doesn't mean I'm not going to write it efficiently.

If I have to store and then do lookups on some structured data I'm gonna use a hash table to store it instead of an array. If I need to contact a DB multiple times I'm only gonna close my connection after the last query. None of this is particularly difficult, but knowing when to use certain DSA principles efficiently falls pretty firmly into the computer science realm.

If you need someone to hyper-optimize some computations then a mathematician might be a better bet, but even those problems are rarely mathematician level difficult. Generally software engineers have taken multivariate calculus/differential equations/linear algebra, so we're decently well versed in math. Doesn't mean we don't hate the one time a year we have to pull out some gradients or matrices though.