Whenever “the phone company” comes out to put in new phones they rip out the existing wire called “a landline” and replace it with VOIP. Which is Voice Over the Internet Protocol. That means that the internet must be up and running to use this protocol. So if the power goes out you don’t have a phone line. Whereas the old “landline” will work even without electrical power from the home. Check out this article.:
The stats from The CDC National Health Services are kept by them
How many people still use a landline phone in 2017?
Income and location have as much to do with landline phone ownership as age.