Apple's stance is that your iPhone is not your, but still Apple's, and you're only renting it under strict conditions.
If they want to release free updates (which I own a copy of) that's fine. If they make me pay for updates (which I will also then own a copy of) that's also fine. If they want to make me sign a Eula to get updates from them, fine I won't sign it but you better have not locked me out of my own device by preventing me from installing other operating systems.