Does your team take your PoC codebase forward through to MVP/production?

I've worked at a few companies where their codebases are quite messy, and it seems to stem from the PoC codebase, which are generally built at a lower standard (no tests, lots of patch solutions etc.), being taken forward. I've always felt that you should start a separate long-term codebase from scratch once you have created a viable solution. I understand this might cost some time at the start but it saves so much technical debt.

I'd be interested to hear how others feel about this