One of the significant problems with systems like automatic speed limits (and lane following, etc) is that they need to work well, and reliably, in all conditions, or they end up posing safety risks themselves. Potentially worse, the implementations often make assumptions based on affluent, developed, modern urban areas, while being implemented everywhere, and so end up being something between a nuisance and a safety hazard in less developed, less modern, and more rural areas.

Driving a rather new car with speeding warnings around the deep French countryside a few weeks ago, for example, when on a motorway, with a speed limit of 130 km/h, the car would repeatedly detect the speed limits on exits, which could mean the car suddenly thinking that the speed limit was 50 km/h until the next 130 km/h reminder sign. Fortunately, the car simply beeped incessantly, and so only posed a minor safety risk in being distracting (the beep could be turned off temporarily, but the override was unreliable). Off the motorway, small roads around ancient towns were often designed with the expectation that drivers would need to frequently drive across lines, so the lane-departure mechanism would frequently engage to try to push the car off the road, or into oncoming traffic (which might be a tractor itself significantly over the middle line out of necessity), though it was fortunately weak enough that it was easy to counteract. And on winding, tight streets in towns, the car's speed limit detection was often significantly wrong, in both directions.

A car, in the middle of 130 km/h traffic, that decides it needs to abruptly slow down to 50 km/h, ending up as essentially a road hazard with cars that could run into it at 80 km/h relative speed, is probably also a serious safety threat, and a system that did that would also threaten your kids' lives.

One might hope that consistent implementation of these sorts of systems would force a realization that they need to work in all places, and that the infrastructure in those places needs to be able to support them reliably. But what I see more often (not just in the EU; the US has similar problems) is that the systems work quite well in areas that 'matter', little is done to improve them in areas that don't (to be fair, sometimes local governments are at least partially at fault for this), the people who live in those areas are forced to deal with systems that seem harmful to them, and the result is an increasing political discontent.