My theory on this. Even though these people were adults. And you thought you they were going to their own homes. They didn't, and the Grim Reaper came and now they have to haunt you until you retire. 😂
Seriously though, I think the game sees the moving out option for adults as the same thing as retirement. This is why they are grayed out and you can socialize with them. They sometimes periodically walk down your street though. When this happens I think you can talk to them.
And inexplicably, some Sims seem to have the blessing of everlasting youth.
Last year, we had a retired Sim who never appeared aged. Everytime I saw her around town, she was in her prime, even though she was long retired.
Who knows. There's a mysterious Sims age programming gene that has yet to be isolated. *shrug*
