Most indie game dev projects start as some small weekend project just to feel things out. Then it starts to become fun so we work on it another week. Then after a couple months we start to think that maybe the game has potential. Then we're 5 years into a project and have no clue how we got there. It becomes a giant jenga tower where moving any one block can completely collapse the whole project, so we learn the hard way that nobody should ever refactor. Pretty much the only people who do refactor end up restarting their project from scratch, getting frustrated because they can't capture their original feel of the game, then ultimately abandon the project entirely.

And for professional game dev projects, it's all built on a foundation of some scrappy little indie project from decades ago.

Some industries are all about making their code public and making it super clean and polished as a point of pride. Games, like movies and sausage, are disgusting to see behind the scenes. They're just piles of scraps and weird tricks that look great unless you get down and examine it too closely. And most people aren't looking that closely, so wasting that time and effort is pointless.