As a counter argument in my day-job I generally assume that the DB will have available disk space and I don't have to worry too much about memory usage unless i

As a counter argument in my day-job I generally assume that the DB will have available disk space and I don't have to worry too much about memory usage unless it becomes an issue (I do avoid naively globbing as much memory as possible but I also avoid premature optimization). Both of those constraints do exist on programming but they don't come up often enough that generally we'll discuss or review code entirely ignoring those effects and instead favoring correctness. Most of the items you listed aren't really important when discussing the nature of a function in the same way the fact that I happened to write my 1+1=2 algorithm on a RISC architecture isn't fundamental for teaching - sure it will potentially behave differently on a different processor - sometimes an intel bug might even cause subtle float errors - but those are implementation details and this article is focused on theory.