There are very large companies, often state owned, who would need to foot the bill to develop this and if they all decide it's not worth it they don't have to worry about anyone getting a commercial advantage by doing it, a sort of unofficial collusion. To get round this you need a maverick newbie (please random billionaire with a heart if you're reading this shake up the market). Fukushima, this gave nuclear a bad name across the globe. Forget the fact that building a 1950s design of generator in an area know for tsunamis was a stupid idea, it still scared people enough to make politicians react by scaling back nuclear, no matter which type.