I recall a few times everyone promised, if this gets promoted then we will rewrite it from zero. Never happened.

Why would you do that though? If you have a working 'prototype' that's handling the demand, has the required features, and doesn't really need to be rebuilt (except to appease the sensibilities of the developers), why would you spend time and effort on that? That makes no sense. The fact it's a prototype or a 'proof of concept' is essentially irrelevant if you can't enumerate what the actual problem with it is.

I work with a bunch of teams that complain that they're mired in tech debt all the time, and complain that it's a huge risk and it slows them down. Except I can see our incidents log and there aren't many incidents and none that can be attributed to running risky code in prod, I have our risk register that has no 'this code is old and rubbish and has past-EOL dependencies on it', and no team has ever managed to articulate how or even how much the tech debt slows them down. They shouldn't really claim to be surprised that no one wants them to spend time 'fixing' a problem that apparently has no impact.

I've also seen the opposite case where a team spent months refactoring an app that they wrote before it launches. They wrote it, then decided they could make it 'better', and spent loads of time reworking most of it before it launched. All the value was delayed because they decided they didn't like their own work. And obviously the leadership team were pissed off about that, and now there's very little trust left.

There should be a good conversation about delivery of work between teams and stakeholders or no one will be happy, but if that isn't happening the stakeholders will always win.