I've wondered about this for years, crossing off theories like you just did with powerful counterexamples.

All I see left is technophobia.

There's a deep human bias. Things we don't understand seem scarier than things we do.

People get how a dam works, the basics anyway. They understand how a car crashes or why it's bad when the pump in your chest stops beating.

They do not like radiation at all. They do not like strange chemicals. They do not like robots driving cars.

They want dangers they can understand, even if that increases the risk substantially.