[Mabusto]

I haven't worked on games in about 10 years, but I wrote core tech for AAA games during the 2000's. Stuff like async I/O, reflection, memory allocation, low level networking, and especially containers were all written in-house. Quite a bit of it was utilitarian, but I agree, a lot was a case of NIH syndrome. Some studios had these insane container libraries that just archived whatever weird data structure someone had as a toy project in university. Math libraries were the same. Scripting languages were all half-baked toy projects by the lead engineer etc.

For consoles, it wasn't that the STL was slow, it was that not all of it was fast, and some parts really were just trash written by whatever the compiler vendor had put together. RTTI was also generally not allowed as it was "slow", and virtual functions weren't allowed at one place because the vtable took up "a ton of extra space". So some of it was cultural, some of it was advice that was ok-ish maybe 15 years before the project began, and a lot of it was just not understanding what was happening under the hood.