First off, welcome to the forum and congrats on the new RV..
1. I would guess it's because of added cost they don't install one. Manufactures want to keep the costs down. A better question is why don't they let you have the option of having one installed when the rig os ordered. I don't have one but then we don't camp a lot in places where the water is bad. We bring gallon jugs and use that for coffee, drinking, etc and we buy bagged ice.
2. Not sure I understand the question. My fresh water water supply inlet on the rig is a standard garden hose size (1/2" hose with a threaded coupling) and I do use a regulator on my water supply hose at the pedestal end. Not sure where you got 1/4".
Stan and Terri
Oak Harbor, WA
2008 Chevy 2500HD D/A
2007 Cruiser CF30SK
Glide Ride Pin Box
Reese 16K Slider