The analogy only goes so far and it's not clear to me what you mean, what do you mean "default on tech debt"? Re-write? Give up and just accept the penalty when changing systems?
Result: you're now stuck with a ton of tech debt and a flimsy product.
Once something is built, and in production in the hands of end users, it is something that needs to be maintained and built on and fixed over time. It's never thrown away.
Now if you are lucky, it has been well-written and designed so that parts can be refactored over time as new features are needed and old ones deprecated. If it's shoddily built and rushed because you couldn't afford or couldn't be bothered to do it right the first time, then that's going to be tech debt you are going to have to deal with for years to come.
(the case I was in was the game Commandos. We completely threw away all source code for the sequel, which we wrote from scratch with different architecture, tech and even somewhat different coding standards. Getting rid of the tech debt that Commandos accumulated over the yearlong deathmarch was nice, but without the completely different architecture needs I doubt it would have happened)