I once did a shoot a GE power and was talking to one of the foremen about the turbines they build (the same kind that fell in the Hudson river a few years back) The things are at least a couple of stories high and about 60 feet long. He told me the run out one the thing was less than a few millionths of an inch.

When I worked for Westinghouse, I was instrumenting steam turbines for start-up vibration analysis. Steam turbine blades are subject to tremendous erosion and stress, so they have to be fairly hard. But hard metal is subject to cracking from vibration. We'd have to determine the natural frequencies of each turbine, and map the RPM where these would develop destructive harmonics.

Steam turbines can't be turned on and off like a motor or engine. From a cold start it might take 12 hours to reach 3600 rpm because you have to idle at several steps on the way up, in order to heat soak. If you idle at an RPM where harmonics are strong, the blades will break.

Then the usual setup is three turbines, with the steam passing through the high pressure turbine, then the medium pressure, lastly the low pressure, before going down to the condenser to turn back into condensate(water). Pump that condensate back to the boiler, add treated make-up water to replace any lost along the way, and start the cycle all over again.

It takes a shitload of piping and controls to do all that, all of which are heavy, bulky, and need maintenance. Buy the diesel. ;)