When they are in “community living”, the DNC can send out knock and drag vans to the “community” to take them to the polls to vote for Democrats. If they were in a State hospital, it’d be harder to get passes for all of them and more oversight to see that they aren’t being “instructed” who to vote for.
That’s exactly what happens in PA. The van for a group home will roll up to the polls. People have reported seeing the patients with cards instructing them who to vote for.