I don't need double bill of home phone and cellphone.
Me, too, neither, that's why I don't have a home phone - wires are so 20th Century.

So what do one due if they use DSL for their internet connection? Wires maybe so 20th century as you say, but I bet they will be there long into the 21st century. The cellphone is not the definitive answer. There are still many places where cellphones DO NOT work or thier coverage is really iffy.