Because it is far harder to use it to create nuclear weapons, there are far fewer political hindrances to mining and trade in Thorium, as well as political concerns over letting potential enemies establish Thorium reactors.
The supplies are also larger, and well distributed, which is also politically beneficial.
Nuclear power is not all about the science.
In the US, for example, the Department of Energy's budget[0] last FY was about 5.5% the size of the Department of Defense Senate proposed budget for FY2014[1] (35B v. 626B).
0: http://en.wikipedia.org/wiki/2013_United_States_federal_budg... 1: https://www.cbo.gov/publication/44459
I have wondered since I first heard of thorium reactor why they weren't already adopted. Since some of the country with the civil nuclear power are those with nuclear weapons, is it possible that the military are lobbying for uranium? (I can see two possible reasons: refining price going down with production scaling, or just to hide their own uranium import in the civil import. If Thorium is adopted worldwide and can't be used to build nuke, seeing who is upgrading its nuclear arsenal would way easier, which can be good or bad, depending on your point of view.)
>The technology development is decades in the future.
Well, that's true for every research domain which isn't funded enough.
Sometime, economy freaks me out even more than politic :'(
The department primarily responsible for the research of nuclear technology including nuclear weapons development is the Department of Energy. Therefore the preferences of the DoD influence DoE decisions.
The thorium fuel cycle has obvious advantages, but it takes so long to transition from uranium to a pure thorium cycle that I doubt I will see it happen in my lifetime.
There seems to be a lot of confusion about thorium. It isn't thorium that makes LFTR so great, it is type of reactor that makes all the difference. Molten salt reactors can run on any fissile material. The only advantage of using thorium over uranium in an MSR is in the fuel cycle.
(Full disclosure: I'm a founder of a startup (http://transatomicpower.com) that is designing a molten salt reactor to burn spent fuel.)