Comment by TeMPOraL

You'd be surprised. In the companies I worked for so far, it's usually my radar that bleeped over ridiculously inefficient code that was present for years in the codebase. That is, some developers would be aware something is off with performance, but they didn't bother to do anything about it. Hell, sometimes even management would know users complain about performance, but the feedback didn't percolate down to developers.

Sure, I get priorities and "good enough". But really, about half of the order-of-magnitude wins in performance I achieved were on things you could find and fix in few hours if you bothered to look. The other half tends to be unfortunate architectural decisions that may take a few days to fix, so I get why those don't get done.