> Having also worked at a few gamedev studios, IME there isn't a real distinction between the two since it is always a matter of time for the former to become the latter.

That was very much my experience at EA, but has definitely not been my experience at Google. While everyone struggles with tech debt, at Google I've worked in many codebases that have been continuously well-maintained with good test coverage for over a decade.

Really, once you build a culture that says, "People not on your team may edit your code without asking and will rely on your tests to make sure they don't break things,", teams get highly incentivized to write tests.