Every place I've ever lived had plumbing in the walls. Now, it also had it in the floors, so your point is well taken. But I seriously doubt that a central plumbing stack is a serious holdup on plumbing out an entire floor.
Then again, I don't have any real experience, so I'm very much being optimistic here without actual hands-on knowledge. I could be very wrong, and would love to hear why!
So, this is me reaching back aways in memory. Walls with plumbing through them are held to different standards to other walls. Walls with plumbing use 2 by 6s. Builders and architects try to optimize by making as few walls as possible walls with plumbing because they are more expensive. Your regular walls use 2 by 4s.
So yes, some walls have plumbing running through them, but not all. Any architect and contractor will try to optimize cost by having as few walls as possible with plumbing. Which is why in some apartments, neighboring bathrooms in units will be close or share some wall space.
I've never seen a wall framed with 2x6s because it had plumbing in it. It's all 2x4 regardless, here—you almost never see a 2x6 wall. Is that a California thing?
The most common example is a wall with a toilet drainpipe. In the US, that requires a 3" inner diameter pipe - the outer diameter is 3.5", which is exactly the same as the space inside a 2x4 wall, but if you need any fittings, it won't fit, and even if you don't, the likelihood of being pierced by nails is too high when the pipe is right against the drywall. If you have a single-story house, there would be no need for such a drainpipe, so this is primarily an issue in multi-story buildings. Sometimes there's a central chase that contains these pipes (as well as HVAC ducting), but unless all your bathrooms surround that central chase, you'll need a 2x6 wall somewhere.
> I've never seen a wall framed with 2x6s because it had plumbing in it. It's all 2x4 regardless, here—you almost never see a 2x6 wall. Is that a California thing?
My California home is all 2x4s everywhere and there's plenty of plumbing in most walls.
Then again, I don't have any real experience, so I'm very much being optimistic here without actual hands-on knowledge. I could be very wrong, and would love to hear why!