There are a million efficient ways to make heat and tons of new development to be made in making heat in new ways. There is relatively very little development in turning heat into kinetic energy and then electricity when size and weight are no object. The combined cycle turbine is incredibly efficient and is likely to continue to be ubiquitous in power generation for some time.
In addition, with our current grid (and many of the things that run on it), frequency is incredibly important. Having giant, heavy, spinny things with lots of inertia does wonders for naturally maintaining a very constant grid frequency as loads fluctuate.
There are a million efficient ways to make heat and tons of new development to be made in making heat in new ways. There is relatively very little development in turning heat into kinetic energy and then electricity when size and weight are no object. The combined cycle turbine is incredibly efficient and is likely to continue to be ubiquitous in power generation for some time.
In addition, with our current grid (and many of the things that run on it), frequency is incredibly important. Having giant, heavy, spinny things with lots of inertia does wonders for naturally maintaining a very constant grid frequency as loads fluctuate.