I'm not sure it's actual regulations, but the Euro NCAP safety tests requiring all these "features" (like not remembering when you turn them off) to get a max score.
Impossible to measure, many other uncontrolled variables - esp. significant improvements to infrastructure in Europe, and regulations. Take NL, where a crash involving a pedestrian or a cyclist effectively forces the driver to prove their innocence. I can walk across a Dutch town blindfolded with the biggest risk to my wellbeing being cyclists (well, and the canals). I'd guess the impact of those intervention dwarfs the "i will beep at you until i make you deaf if you don't put your seatbelt over your grocery bag" innovations.
I grew up in/with cars which would score 0 (more like -3 to -5) and made it to adulthood, so I have a feeling that these features are not strictly neccesary.
At the same time what if it saves at least one life a year? (same goes for riding with/without helmets)
Everyone dies eventually, so that means very little by itself. Did they die young? How much younger than their peers? Did they gain enough enjoyment from drinking and smoking to offset the fewer years of life (subjective, of course, but important to consider)?
Every intervention has a cost. Not all results will be worth the cost we pay for them. I think we are well past the point in Western society where we are giving up too much in order for too small a return, personally. With cars, but also just in general, people have lost the ability to do cost-benefit analysis and act as though every safety improvement is an unalloyed good. But they aren't, and I think that this thinking is making all of our lives significantly worse.
Given that its society that invests in them during development and has to pick them up when they're broken its only fair to also nudge towards a preemptive solution. The economics of people dying needlessly in their 20s is worth the intervention.