This is how apps on phones worked for a really long time, each carrier ran its own App Store and in many cases you were renting the phone from them or getting it for free with your plan. Mobile carriers have begun merging into megacarriers over the last decade, but for a while you had a choice of at least 4 real carriers in the US.

Plus, you could unlock your phone (in some cases) and move to another carrier, which theoretically meant a different store! True freedom.

Of course actually using these phones and putting apps on them was MISERABLE, mostly because they were symbian and/or j2me apps