Because the company's internal rubric for performance reviews awards 0 points for this kind of work.

You answered yourself.

Maintenance is seen by business as a cost, innovation is seen as potentially bringing more money. The incentives are all wrong and that translate to engineers (and teams, and companies) chasing features and not fixing bugs.

A rewrite is often the only way of getting enough resources to fix up things.

They should value both but just don’t in my experience. Building a system can get you promoted. Performing maintenance to keep it running generally will not. Doesn’t matter if the maintenance project demonstrates a higher level of proficiency than the original development. Doesn’t matter that it’s extending the life of a system providing known value, as opposed to building something with theoretical value.

Of course they should, but it just doesn't seem to work out like that.

I was basically pushed out of my previous job because I was the bug-fix guy and liked it.

When I was the 'new stuff' guy, I got big raises every year. When I moved to being the bug-fix guy, and other people were the 'new stuff' people, suddenly I stopped getting good raises and barely met inflation. Even my coworkers were heaping praise on someone who I knew was over-complicating things because he was doing new stuff.

As I was leaving, a system that I had rewritten twice was up for another rewrite for more functionality. I would have loved to do it, and I knew I could. They gave it to someone else. I heard, 6 months after I left, that they failed and gave up on the rewrite. I am absolutely certain I could have done it again.

Getting a new job got me a 40% pay raise. It's not that I wasn't still worth a lot more every year. It's that they couldn't see it because it was all maintenance, and not shiny new stuff.

I still prefer bugfixes, and I still rock at them. But I end up doing mostly new stuff and don't say anything because I know how that goes.