There are technical reasons, but as ever the real underlying causes are incentives. Companies realized that the OS is a profit center, something they can use to influence user behavior to their benefit. Before the goal was to be a hardware company and offer the best hardware possible for cost. Now the goal is to own as large a slice of your life as possible. It's more of a social shift than a technological one. So why would a company, in this new environment, invest resources in making their hardware compatible with competing software environments? They'd be undercutting themselves.
That's not to say that attempts to build interoperability don't exist, just that they happen due to what are essentially activist efforts, the human factor, acting in spite of and against market forces. That doesn't tend to win out, except (rarely) in the political realm.
i.e. if you want interoperable mobile hardware you need a law, the market's not going to save you one this one.
But, I'd guess this accounts for a relatively small fraction of corporate decision on lock-in strategies for rent extraction - advanced users should be able to treat their cell phones OS like laptops, with the same basic concepts, eg just lock down the firmware for the radio output, to keep the carriers happy, and open everything else, maybe with a warranty void if you swap out your OS. Laws are needed for that, certainly.
My guess is that modern hardware is too complicated for one hacker to write reliable drivers. That wasn't the case back in the 90-s, when Linux matured. So we are at mercy of hardware manufacturers and they happened to not be interested in open upstreamed drivers.
On any PC, you can still use BIOS/UEFI services to get a basic framebuffer and keyboard input. You cannot do that on embedded ARM devices - you need to get several layers into the graphics stack to have a framebuffer. I tried it on the PinePhone, using existing source code as a reference, and the furthest I got was sending commands from the video port to the LCD controller and then not having an oscilloscope to see if the LCD controller replied back.
Because that's what customers want to buy. People are paying premium iPhone prices for hardware with mediocre specs and then the hardware sells out when someone like Purism or Fairphone actually makes an open one. How many sales would you get if you did the same thing on a phone that was actually price/performance competitive with the closed ones?
Meanwhile all of that "profit center" talk is MBA hopium. Nobody is actually using the Xiaomi App Store, least of all the people who would put a different OS on their phone.
The real problem here is Google. Hardware attestation needs to be an antitrust violation the same as Microsoft intentionally breaking software when you tried to run it on a competing version of DOS and for exactly the same reason.
Having basic framebuffer in BIOS/UEFI is neat for toy OSes, but not very relevant for something practical. You gotta need proper driver for GPU. And if you're just starting, UART console is actually more preferable way to interact with board, IMO.
Modern hardware has turned our operating systems into isolated "user OS" nodes in the schematics, completely sandboxed away from the real action. Our operating systems don't really operate systems anymore.
Yes!! Absolutely agree. This needs to be made illegal.
Plenty of adversarial countries have a competent security service. A foreign government can compromise the corporation's root signing key for the devices through technical attacks and through bribery, espionage, physical intrusion, etc. And they're not going to tell you that they have before using it against your high value targets, so how do you protect them? By not relying on systems with a single point of compromise.