Ass properly covered, I'll be real: I'm never surprised to see this because "code reuse" is generally the sign of reasonably advanced developers and I don't know a single person in game development I would hire for a role outside of it. It's not just NIH--that's a problem but one slowly going away. It's more just a fundamental lack of understanding of software engineering and building Good Code. As time goes on I've seen gamedev acquaintances poorly reinvent most of the wheels that the rest of the world takes for granted--even something as simple as serialization for save data and network transport (but no schematic validation, because "schemas suck") was trumpeted to me as this Big Crazy Great Thing. Which contextually it may be, but I kind of feel like the state of the art for stuff not involving pointer munging is about a decade behind everybody else.
So, code reuse? Gotta make good code first.