I would note that motorcycles, ATVs, tractors, etc. still don't have seatbelts or airbags. And sure, that's partly because, for some combinations of safety feature x vehicle class, they fundamentally can't. But we could have just outlawed public road use by those vehicle classes because of that. We didn't, because the lack of much more basic safety features (e.g. a roll cage) was already "priced in" to our decision to allow those vehicle classes on the road to begin with. These vehicle classes represent different trade-offs in safety-space, that operators of all vehicles sharing the road are highly aware of, maintaining a sort of mutual understanding of vulnerability of the different types of vehicles they're sharing the road with.

(That is: it's not just that motorcyclists themselves are more aware that they could be fatally T-boned (and so drive more defensively / keep more distance to avoid that outcome); it's also that drivers of heavier vehicles who encounter a "trolley problem" where they can either veer to hit a car, or to hit a motorcyclist, are aware that there's far less metal protecting the motorcyclist from the impact — so they are very likely to choose to veer to hit the car instead.)

And because of this, I would expect that we would never truly see the elimination of speed-limiter-less road vehicles, even if all cars were mandated to have them. There's just too many other things on the road (motorcycles, ATVs, tractors and construction equipment, e-bikes, etc) that are designed with these different safety trade-offs, such that they would likely never end up having the speed limiting imposed on them.

And that's enough things still on the road that could be dangerous if they hit someone, that would need to be pulled over for speeding, that I wouldn't imagine we'd see "off-board" speeding enforcement go away any time soon.