Im gonna be the AkShUalLy guy here and say this isnt always the case….
There are shower controls that turn on immediately to full pressure and then adjust for temp as you keep turning, no way to actually control the water pressure without just having fully cold water. These have been around forever…
I installed a newer Delta one in my house a few years ago (2021 or so). They now have a feature where the water temperature is always whatever you set it- no fluctuations of scalding water when someone flushes a toilet or random freezes if someone turns on hot water elsewhere in the house. Or even 2 showers/baths fighting for hot water at the same time. So it’s like an auto-adjusting thing that happens inside that requires max input pressure to work right. Of course, i always want max water pressure, so this was a win-win for me!
To note- this wasnt a crazy expensive, high-end model…it was basically what most of the single knob/lever shower controls are now.
Huh, I grew up with those and thought everyone had them, except somehow people we visited
Now decades later, my shower doesn’t have that function. However it doesn’t matter because there’s only one bathroom so you’re not likely to get pressure changes (I also thought it was normal to have 3 bathrooms)