Its the frontier of reactors-that-don't-explode. In the short term, our laws were written with light water reactors in mind, so anybody who wants to build a thorium reactor is going to have to build all the same expensive safety features that light water reactors need, plus the special metallurgy that molten salt reactors need. So basically it doesn't make sense until something changes.

Thorium has some potential advantages and some disadvantages. Overall it's a mistake to imagine that it's some sort of nuclear energy free lunch.

Thorium reactors are often MSR designs too. But if this offers the possibility of reducing our existing waste supplies, it might make it more publicly palatable.

80% of the cost of nuclear energy is building the reactor. With around $500B worth of existing reactor infrastructure worldwide, which runs on Uranium, don't expect that to go away too soon.