Ironically, a major reason for this is environmentalists themselves. Nuclear power would be way cheaper if it wasn't for their panic over things that contain atoms.
In terms of safety, there's a big difference between nuclear technologies that fail elegantly like LFTR and more traditional designs that tend to use weaponized isotopes with very long half-lives, and can meltdown and explode when operated incorrectly.
I can understand why environmentalists look at Chernobyl and Three Mile Island and say, hmm, maybe we shouldn't do that.