If anything the open source community is a lot better in supporting large numbers of devices than closed source has ever been. Witness the incredible hardware support in your average linux kernel. The only reason they're a bit behind the times is because hardware manufacturers are loath to open up their specifications to open source implementers.

> The fact that I can pick up a PC from the nineties and install an up to date Linux

See, that's exactly the reason why this works.

1) One volunteer spearheads the development effort towards keeping phone/tablet/device X supported. 2) Various other people draw on the 90% base work already done by Lead #1, add their own wrappers, tweaks, etc, such that the community on the whole appears to be vibrant and bustling around development for device X. 3) Lead #1 eventually stops supporting the project because he gets a newer device. 4) None of the developer's behind Lead #1's forks have sufficient technical knowledge to continue the base development without him, and all of their forks stop updating as well. 5) Community on the whole for Device X fizzles out.

I've seen it happen multiple times on XDA-developers forums. That dozens/hundreds/thousands of people are using an AOSP-based ROM on a device does not mean that the community necessarily has the technical knowledge to continue it without someone to steward the project. The volunteer leads do an incredible job, but at the end of the day, they usually only last as long as the device is the lead's daily driver--after that, they usually stop.

Not entirely true. The mobile hardware ecosystem is vastly more diverse than the PC ecosystem.

For starters, there was never any cloneable, de facto standard (a la IBM) thus everyone started from divergent designs.

Add in the limitations that PCs never had to deal with (miniaturization, power, cellular radio integration) and you rapidly get each company integrating things as quickly as possible so they can get a product to market.

And honestly, there's not much reason support clean code underneath the hood. 99% of your customers will never flash a custom ROM, much less change the OS. If your stuff works, and you've got the time for a rewrite for the next model, full steam ahead with business as usual.

Unless the SoC drivers are mainlined, you won't be able to upgrade your kernel on such a device. This is precisely the same issue with Android where people mistakenly blame Google instead of Qualcomm (driver authors) for the lack of Android upgrades.

Does this also apply to iOS devices?

With Android you have the Linux kernel team providing the mainline kernel, the SoC team providing the drivers, and Google providing the rest of the OS.

If the SoC team don't care about mainlining their drivers then those devices will only ever support the kernels that the SoC vendor releases packages for.

If Google wants to move Android along to a newer kernel and the SoC vendor isn't playing ball it comes down to hacks that may be acceptable in a community ROM but I wouldn't want to support in a commercial device.

Great point about how PC hardware can always be expected to be generic enough​that we can just install Linux on it and not have too much trouble, yet there is no equivalent for phones, but there really needs to be.