I am not convinced this is always true. The first 25 years of my career was spent making games. Never had tests. We had testers but no tests. I then worked at a big company with tests. My first experience with them. Working on something important I loved them but they easily cut my velocity by 70% compared to what I used to get when working on games. The games were AAA and shipped to millions of customers on CDs and Cartridges so no bug fixes allowed after the fact. Being a big company and big project there were 10-30 engineers who's maintained testing infrastructure, continuous integration, etc. That's larger than the entire engineering team on most games I worked on.

I'm not arguing against tests and having had the experience of testing I'd use them when appropriate I'm just not sure the exact cutoff. If I was working on a game engine for multiple teams I'd be writing tests for sure. If I was working on a small 5-20 person team with custom tech I'm not sure I'd start adding tests where I didn't before. Maybe if there was IAP or multi-player online or some other server component and metrics. Or maybe if it was easier to get started and maintained.

Theres a bunch of big differences with games vs much other software. Often games are not maintained after shipping. Of course that's less true today than it was in the past with longer term online games but it's still also true that many games area pretty much done the moment they ship. Another big difference is the teams are 70-90% non-engineers making tons and tons of data.

I mostly bring this up as that often software engineers talk past each other since no all software engineering is the same.

https://www.joelonsoftware.com/2002/05/06/five-worlds/