I have had accidents, once because I was too close behind someone (never do that again) and once because the car had a bad tyre that blew out, and I came off the road, over a ditch and ended in a field. I was lucky to survive and lucky not to hit anyone else.
I was glad in that case that I was wearing a seatbelt, it definitely safed my life - but who's to say I might not have driving a little slower, a little more carefully, if I hadn't been wearing one? I don't know. I might have hit a tree and died anyway, seatbelt or no seatbelt. The point is that (I believe) the feeling of safety and security behind the wheel - and the consensus seems to be this is real safety, not just the perception of safety - does make people behave more recklessly, that Nah it'll be fine feeling we all know. If we weren't wearing seatbelts in the driving seat, would we take those risks? Would we drive at that speed?
I think the safer we already feel at any given moment, the more likely we are to take risks at that moment, and the more risky the risks will be that we take. It's just an opinion, not a particularly controversial one, and I think it applies to driving as to any other risky thing that people do. More broadly I have a theory that more security exists everywhere around us the more H&S applies everywhere, all the time, the less mindful we gradually become about the risks that do exist and our approach to them.
tl;dr - the more protected we feel the less we look to protect ourselves.