I think the reality is that some people are actually just fine doing the maintenance - but they're unlikely to boost their career/paycheck by doing so comparable to what they'd have gotten from making a new thing instead. And that's an issue.

I'd love to go back to old code with the benefit of deeper domain knowledge and greater understanding of my tools and be able to make products even better. However, it's hard to square that against making +20% earnings by helping build a new chat app.