I think the kind of surface level rewrites that people rag on are pretty rare, at least in my experience. Realistically code that's impossible to understand, underdocumented, and lacking in proper abstractions is also deficient code. If you've ensured that the code is "good enough", you will likely hit a bug or feature request that is hindered by the poor structure and understanding of the code.

It's totally fine to say "the code works, that area is stable, let's not mess with that code". I make those kinds of tradeoffs on a near daily basis. But let's be real, "perfectly functioning code" is an ill defined, moving target. What looks like perfectly functioning code to a sibling team or a PM, could be a massive liability to someone who actually knows the code.

But then again I'm writing OS and performance critical code. A 1 in 1 million bug is easier to ignore in a throwaway log viewer website.