But the current accepted standard of how ARM devices boot, specifically how you're reliant on an image you have no control over, ends up just generating a ton of devices that can't be updated when the manufacturer decides they don't care anymore. I'm not just talking about phones either. Handheld (gaming) devices, Pi knockoffs, network gear, even real Pis to an extent. Most of these devices it's very easy for the hardware maker to go "oh we'll just run our own patched uboot" and when that image needs updating you're 100% reliant on them.
As we know, this means that the company will drop all support, usually within a year or two, and ask for more money to ship you a new thing across the world. This is not acceptable. No, I don't care about your "oh well this company still gave me an image!" example, the point is we shouldn't need to rely on the original hardware manufacturer to maintain software updates.
Until there's a standard boot process that is at least open enough to prevent devices from becoming e-waste (ala UEFI), they're trash on borrowed time and should be avoided as much as possible.

