There are ways to solve this without killing off the ability to root phones if this was really about users' safety. You could for example make it so that phone

There are ways to solve this without killing off the ability to root phones if this was really about users' safety. You could for example make it so that phones could only be unlocked within a few days of the purchase (first boot) date, and put a scary warning on it. That'd put a stop to 99% of people being tricked into unlocking it. You could also put a scary warning on boot that allowed anyone to tell it was rooted to stop people selling them while rooted. The point of blocking rooted phones isn't "security", it's to maintain control of the user experience.