How is that inherent? That's something they added to the device to restrict our options. Now even if we accept the argument that this is necessary for security, why is there no provision for the owner to add their own keys, or bypass it explicitly?
It's inherit because that is how the device was designed to function. Ultimately it's just silicon, so there isn't a default design for how it should work.
Developing a restrictive feature at significant cost and imposing it upon the consumers isn't nearly what a reasonable person would consider as inherent or default. You can argue otherwise based on technicalities or arbitrary definitions and that's what these companies have been frustrating the consumers with. However, such gas lighting is the what justifies the hall of shame, skip lists and name and shame pages and websites like these. I'm hoping that they catch on in popularity because this sort of tactics deserve equally harsh disrepute.
It is a tablestakes security feature. And adding an additional feature to support swapping keys has an additional cost and adds complexity to the design.
Now you're just shifting the goal posts. Locking down the full root and the firmware from even the owner, while retaining an exclusive remote exception for yourself (the OEM) at the same time is worthwhile, but adding or swapping user keys is too complex and costly? Forget the fact that this isn't nearly as complex as what they've set up for themselves. This is the bare minimum that an OEM is obliged to provide the owner, when they lock down the device. They're able to get away without doing that because the market isn't free or fair anymore. They twisted the market and the regulator to unfairly benefit them.
Now we are going from gas lighting to just making up excuses to justify what benefits you (the OEMs). This is exactly what I've been accusing them of, all the while. Their justifications are technically false, misleading, arbitrary, unfair, shallow and opportunistic.