> teach apps who they should trust

Ah, the apps^Wgovernment (look at that page, most of it is government IDs) should be able to discriminate against me for daring to assert control over my own device. And GrapheneOS is saying:

Hey government! We pinky promise to oppress the user just the same, but even more securely and competently than Google/Samsung!

> what does it matter to you

It shows that the developers maybe don't fully have your best interests at heart?