Not a decision based on science.

Is it an honor system? Trust on people's consciousness?

If you believe mask is necessary then:

How do you tell who is fully vaccinated? There is no verification system on top of nothing to verify against (no national DB) on top of fake vaccination cards.

With only 1/3 of the US population vaccinated, and resistance from almost half of the rest (guesstimate, from hoax to conspiracy theories to not trusting any vaccines...), it will be like this: no mask required, period, there is no if.

Either the virus is tired of spreading and is looking forward to its own retirement or spikes of variants will come