There’s big differences between all of these:
- New construction, no walls installed yet.
- 1 or 2 story with unfinished attic and unfinished basement, preferably mostly square shaped.
- Finished basement restricting access. Coupled with a not square footprint.
- Finished attic space.
- House old enough to have coax but not ethernet. Or, someone already did the coax retrofit age.
- House so old, it’s lucky to have electricity, and you’ll be running something no matter what.
It’s not that you can’t add new wires, of any type, to any of these types of houses. But, there’s definitely different amounts of work and destruction to do it right in each of them. Hell, even doing it sloppy can be a pain, unless it’s truly super sloppy. I’m looking at you 100 foot ethernet cable strung down the hallway, up the stairs, and across the hallway, try not to trip on it. 
As much as I hate Verizon in general, and what the hell are all those “fees” on top of the basic service. The network access has been super good, and looking for the ONT was part of our house shopping. (Looking for the ease of adding new wires didn’t make the list, at least not high enough in priority.)
