With overlays you can get a situation when two members of a household have two different area codes.
I know of that happening with cell phones, when a mother and son signed up with the same service, AT&T, but at different store locations and got different area codes. Today they're no longer in the same household and neither of them lives in the area code they were given. I don't even look at telephone numbers, and if I see one, I just see a ten-digit block that tells me nothing about where the person is, or even where the person lives. I remember knowing area codes and prefixes telling me what town a person was in, but that hasn't been the case in years.
We need to go back to when you had to pick up an ear piece and turn a crank to alert the operator, and then tell her that you want to talk to Mr. Drucker at his store. That way you don't need to worry about numbers.
Oh, wait, we already have that, and it's fully automated. So who the hell cares?
The only thing I care about is not forcing anyone to change their phone number. Cell phones accomplish that for most people, but if a store moves across the street to a different area code, they shouldn't be forced to change. It's not like anyone else is using the old number. It would be silly to make the store clerk run across the street and climb up the pole to answer the phone just to be on the right side of the line so they can keep their number. Area code splits are, of course, a much worse form. If you move to a different state or a hundred miles away and want a landline, that's different.
I was the nerd who knew everyone's telephone number 30 years ago, including the distant relatives no one had seen in 20 years and I'd never met. If you want to memorize telephone numbers today and dial them (punch them in manually), you're free to do that, but even if you do that, with ten-digit dialing being everywhere, what (beyond technical limitations of landlines) does an area code even mean these days?