This can be as simple as isp peering arrangements between services.  If you
use Cox Residential, you egress out LA for all internet traffic.  If you
have Cox Business, you egress in Phoenix still, which if you vpn to local
things, that is good.  Up to your provider and their service contracts
usually where you end up leaving your particular walled garden.

Cellular is usually even more shady with mobile IP arrangements, where your
phone usually has multiple addresses and carrier-grade nat is used
extensively.  You get highly virtualized basically, so location becomes
moot (unless the government wants your gps coordinates, well then...).

My cell service with StraightTalk using an ATT sim in Peoria has gone
significantly worse the past year or so, as they moved a main tower further
away.  Now even sitting in my office with a window facing the tower
direction it's wonky as it's a few miles away vs. before less than a mile.

-mb