> The telephone system's address plan embedded a certain amount of physical location information in the fixed line network, and a full E.164 telephone number indicated your location in terms of your country, and your area within that country.
Until quite recently (i.e. with the introduction of NGNs), it's my understanding that in the US, calls to mobile phones were (and probably often are) still routed to the geographic location of the phone number's rate center.
People don't usually think about it because intra-US latency is usually low enough to care (and lower than the latency to most outsourced call centers in any case), but during natural disasters such as Katrina, the ties between geography and network topology still make themselves known.
The US mixes up fixed line numbers with mobile numbers, so you can’t tell them apart based just on the number.
In Australia, mobile services are a separate area code-so a mobile number tells you that it is a mobile number, but nothing else-once upon a time, the first few digits told you the telco, but with number portability that is largely no longer true.
Unless it is the teachers at our kid’s school, who use Microsoft Teams to call parents on their mobile, so it looks like it is coming from a fixed line
Some of it is probably an artifact of mobile plan pricing being quite dependent on who you were calling when cell phones became widely available. I (still) have an area code that's the result of who I tended to be calling on my cell at the time. Hasn't been my "home" area code for many decades. (Not that I actually have a landline any longer.)
I think it's the other way around: Since calls were routed geographically, and it's not apparent to the caller whether they're calling a landline or mobile phone, it also made sense to price them geographically (at least before the marginal cost of the incremental call-mile went to zero).
I didn't actually even live in the area code at the time but had outdoor activities with people who did live in that area code who I might call from my cell. So that's what I chose. And, by the time I switched carriers, phone number portability was a thing.
Funnily enough, that area code became something of a status thing in an era when near-in suburbs got "kicked out" to a suburban area code when a lot of people were getting second phone lines for modems. There's a Seinfeld episode related from a different city.
vs. modern reality
https://xkcd.com/1129/
(And who hasn't experienced a Customer Support phone number that is answered in different parts of the world, based on the time of day?)