It's amazing how many great ideas have been abandoned because builders were doing things on the cheap.
The home my parents built in the early 1950's had a removable panel to provide access to the bath tub plumbing. Don't know if that was just something my dad opted to do (he was a pretty practical guy), or if it was customary at the time, but it really was a great idea.
When our current home was built (20 years ago), the builder didn't even bother to provide attic access - I suppose he saved around 35 cents by doing that,, but I would have gladly paid a few hundred bucks for that feature if had given me the choice (or if I had thought to ask for it).
In our former home (which was built in the late 1940's) we had a problem with the tub in the downstairs bath, and of course, there was no way to access the plumbing. After working on the plumbing, I made a plywood panel to fit over the opening, and painted it so that it wouldn't be so obvious. A little trim moulding disguised the fact that it was a patch. As far as I know, it's still there - we sold that house 20 years ago, and its been through at least three owners since we left.
Later, when we added a second floor bath, I put a linen closet at the head-end of the tub, and designed the framing and wall so that a large section was removable just in case I ever had to get in there. And since there were some plumbing fittings under the closet floor, it was also constructed to be easily removable. I never had a chance to tell the people we sold the house to about those openings, so the current owners may not even know they are there.