Right now the biggest problem is that it's really expensive, and takes a long time to build. Investing billions that won't start pay interest for at least 10 years isn't attractive to banks that need to show a profit every year, or governments that have to face an election every 4 years.

That's one of the reasons why small modular reactors are interesting. You don't have to invest so much before you start to see a return.

It's also why wind is doing so well. It's easy to borrow the cost of a turbine, or even a wind farm, and it starts making money pretty quickly.