Most boats seemed to have normal, "nice" shower heads (5gpm or greater) instead of low flow "Navy" heads (1-3gpm) and thus I never felt the slightest bit of guilt about any shower I ever took.
Let's see, 300~ish people on a smallboy crew, if everybody is hustling and uses only 5 minutes of water a day, these things will save the ship a few thousand gallons of potable water every single day of cruise. That's using conservative numbers.
They're also cheaper.
"Don't take Hollywood showers" is one of those clarion calls of hurr-durr leadership, same as things like the guy at the safety stand down who says to always drive the speed limit for safety. FWIW the Army was just as dumb in their hardware choices for field showers...