They sort of do, or they do in a way that makes them almost useless once they hit their final low level. Are you suggesting that instead of asymptotically going to zero, they just hit zero at some point?
The most annoying thing about a nuclear setup is needing to have space to put it next o water so you can pump in the multiple lines of water to each end of the operation.
The space the pipes alone take is often as wide as half the full nuclear operation also