You should care about security updates. For most people, their phone has more very private data than even their laptops. And the attack surface on modern phones is absolutely massive.

This would seriously be a Killer Feature for phones for my parents. Android updates confuse the hell out of them (me, too, when I have to help them out—Google's UI design for their built-in apps is terrible, and they can't help but screw around with it in unhelpful ways every single release)

LTS Android (or iOS) with five+ years of security-only updates would be the perfect phone for them.

You seem to be contradicting yourself?

I took the original comment as sarcasm.