> I feel like the only explanation here is that the smartphone duopoly has worked hard to condition customers into accepting this.
This is older than the current smartphone duopoly; IIRC, with a few exceptions like the N900 and the Palm Treo, cell phones were always very locked down. It probably came initially from the phone companies being control freaks, and wanting to restrict which devices (even mechanical ones with no electrical or radio interface) could be attached to their phone system.
Yes, phone companies did not want this parties devices attached to their analog network, which basically was a low voltage power grid.
I don't know if we can say that those old phones were locked down: either they could not run any software at all or they run only what they got in their factory settings.
Symbian phones, palmtops from the 90s and the like could run apps and I did write a few of them. Usually Java and an emulator on my computer and an upload to the phone. They were almost general purpose computing devices but it was hard to get a 30% tax on them. All of these policies from Apple derive from the will of making money from services, not only from the hardware. It's understandable because it's a lot of money.
If apps will ever start losing money to Apple (e.g. they are forced to distribute them for free), apps will be dead, the Store will shut down, nothing could be installed anymore (privacy, safety, think of the children) and everything will be done with a web browser.
This is older than the current smartphone duopoly; IIRC, with a few exceptions like the N900 and the Palm Treo, cell phones were always very locked down. It probably came initially from the phone companies being control freaks, and wanting to restrict which devices (even mechanical ones with no electrical or radio interface) could be attached to their phone system.