Ahh but you eventually will (at least in my experience). If you don't need to the code either doesn't matter (dead code) or works just fine.
I think I have looked at my own companies entire code base a couple of times. Do I see nasty crap... all the time. And I often fix it for good taste when it is really bad but I have to say the value prop isn't very good compared to adding tests or other automated validation (including automated profiling and dead code analysis).
Kernel code and in particular C are sort of special cases because they are hard to test and performance is generally a high concern. But for many other higher level languages and problem domains this is not the case.
I have been meaning to look how at how much code bases change overtime. In the case of Linux I wonder how much of the Kernel code has stayed the same (lets say over a 5 year period). Probably not a ton but I bet for other domains particularly business software the code either just dies or changes dramatically over time.
Then there are I suppose other domains where the code really can't physically change often (ie space probes and embedded devices).... for those systems I really really hope they have lots of tests.
Yeah, but you won't. I think that's part of the reason why people care about "taste". I want to maximize the chances that essentially the first draft is good enough to be maintained for as long as possible, because years of hard-won experience has taught us that it will.