Streaming is a major use case where the camera may be recording continuously for several hours at a time. Another one is for video meetings, though in that case I’d prefer it if my camera forced the end of the meeting after 30 mins.

Camera manufacturers can just enable the functionality as an easter-egg.

So they just publish some activation code on some consumer forum somewhere and from then on it's the consumer's responsibility.

I think they did the same thing with DVD region restrictions.

I can’t see why you think there’s a usecase for 25 minute videos but not 35 minute ones.

Speaking as an amateur photographer with multiple DSLRs: I’ve certainly needed longer than that for a number of gigs.