And they won't let anyone install any other software onto the hardware, so I can't even rely on the free market providing what I want.
Because otherwise you won't buy new device for full price
Imagine the cool things people could do with old iPads. Put Android or Ubuntu Touch and give it to people who cannot afford a tablet. Wall display for Home Assistant. Rip out the batteries and have a very low energy ARM server, etc.
If we're talking about a 15-year old device, it definitely feels like requiring (1) a boot loader unlock method & (2) all technical specs required for basic functioning (display, input, compute) aren't overly burdensome on Apple et al.
Essentially mandating a corporate 'methods and specifications' EOL requirement to avoid device obsolescence.
This would also have a side effect of giving the EU a regulatory trade barrier against sketchy fly-by-night Chinese tech (e.g. "DMOAO tablet").
And encouraging tier I tech device manufacturers to offer longer warranties, in their own self-profit-interest.