I'm the IoT node design space and this is what we use. There is no sales or use case to repurpose the device one it's at the end of life, and we don't want people to do as such.

The point of secure boot is to make sure it's only our firmware running, and only our firmware connecting to our backend with the appropriate keys. Anything else is a security nuisance at best and an company killing problem at worst.

We're willing to sacrifice the SoC in those cases. Your mileage may vary.