Excessive Steam Syndrome (was: Stanley Steamer Space Ship if you wondered about the alphabetization): Even those reactors that use other principles to extract energy still harness the thermal differential they produce, because it’s there and not to be wasted.
Meanwhile, spacecraft require their own complex cooling infrastructure, and often use cryogenic fuels which will produce plenty of condensation around the piping, and have pressure-release valves as does life support, and there are quench valves on superconducting systems, and so on and so on and basically, there is plenty of water vapor, et. al., to go around to produce this effect when machinery happens to be located within the pressure hull.
At least you only get a little inescapable condensation and vapor (from moisture in the air) unless something’s leaking or popped a safety valve. In normal operation, virtually all the rest of of this stays on the inside of the tanks and pipes, where it belongs, rather than ruining your entire day the way superheated-steam amputations or being flash-frozen solid by deuterium slush tend to do.
(Also, yes, just like NASA et. al. many planetary starports do use a gagillion gallons of water to sink the heat that launching reaction drives dumps into the pad. Non-potable water has the virtue of being essentially free on many classes of planet.)