I don't know about the rest of you but I got into software development to create software (ideally from scratch) and to learn clever new stuff, not to tinker with someone else's code. Of course, just like every other software developer, I have on occasions ended up working in someone else's codebase. But I have done this not out of choice - and except in a handful of cases, I have not gained any knowledge or mental satisfaction from doing so. I have done it because I have been told to by my boss.
Let's not con ourselves. Becoming a dab hand at maintaining other people's software does not make you a good software developer (writing your own software does that). It makes you a good employee who is willing to do the boring shit. The two are not the same. I for one hate maintaining other people's code, and if I ended up doing that the majority of the time, I would either get a new job, switch careers or kill myself. Probably one of the first two.
I think you're missing the point. The idea isn't to have to maintain someone elses rubbish code.
The idea is that reading good code makes you a better coder. Which it certainly does. Having said that, bad code can sometimes teach you lessons in how not to do things.
At some point in your career, you come to realize that unreadable code is bad code -- and that if you aren't writing readable code, you are a bad coder. Usually this realization comes when you are asked to fix something in code so horrible that it causes you to wonder aloud, "What idiot wrote this?" And you look in the repository logs and see that it was you, several months ago.
Even if you never intend to maintain code, if you don't want to be that guy whose code everyone hates to work on -- whether out of compassion for your maintainers or out of career self-interest -- you need to know how readable your code is relative to others'. And the only way to know this is to read other people's code.
Let's not con ourselves. Becoming a dab hand at maintaining other people's software does not make you a good software developer (writing your own software does that). It makes you a good employee who is willing to do the boring shit. The two are not the same. I for one hate maintaining other people's code, and if I ended up doing that the majority of the time, I would either get a new job, switch careers or kill myself. Probably one of the first two.