OK. There were also 640x400, 640x350 (EGA) and 1280x1024. Under Windows, also "Small fonts" and "Large fonts", which changed size of controls, but not bitmaps.

Each of these options gives you something. Focusing on single resolution (or fixed-number multiples) is short signed, almost like basing your's OS binary API on soon-to-be obsolete and unstable C++ ABI (I'm taking shots at BeOS - they took the easy solution at the beginning and what problems it caused).

Especially when the system has the tools to handle the differences.