[fsloth]

"I'm not sure it makes sense professionally, though, as most codebase won't survive a decade"

That is highly context sensitive. For example CAD packages are generally decades old.

They can't be rewritten from scratch. There is too much code. Too much of it is domain specific. The features can't change or else customer projects worth billions might suddenly go tits up when they migrate to a newer version (customers don't migrate to newer version very often though).

So, if there is some domain specific use case, worth millions to the software vendor and potentially billions to clients then stability is far more critical than keeping the codebase "modern".