This is a good point. I'd like to eat something tasty each day, and I know that my chances of being successful at that would be improved if I made myself the dictator of the Earth. But currently there are far easier ways of making sure that I get something to eat each day, so I don't bother with the dicator scheme with all of its associated risks.

Of course, there are various counter-arguments to this. (Some minds might have a much easier time of taking over the world, or perhaps more realistically, might seriously underestimate the difficulty of doing so.)