Apples and oranges. The 2020 (budget studio condenser) has a totally different application from the SM58's (mainly live vocals, general all-rounder, smash it into a punk singer's forehead and it still sounds fine). The thing about the SM58 is that it is the standard, for better or worse, and that makes some things easier when you're working with different people, because everyone from vocalist to sound tech is familiar with how to use it effectively.
The SM57 is one of the best bang-for-buck microphones - it's used in top studios with unlimited funds, and on every stage in the world. Maybe not ideal for all applications, but it's tough to beat for miking a snare drum or guitar amp.
True enough, I just had one on hand when I started doing stuff that involved mic's.