I seriously wish that followers had an option to return back to their home locations. I learned that you could do this in vanilla by not picking a location for them, but I learned this too late. It should be an option for them in their personal travel menu called (Home). Followers can clutter up settlements and/or break the immersion, just like Handcock hanging around in Sanctuary when he should be running Goodneighbor. Maybe its just me, but this is annoying.

Hancock is intentionally avoiding Goodneighbor if you do his quests, but people like Danse and Piper have story related reasons to be back in their original places.

I have most companions at Greygarden and few at Castle. Only 2 at Sanctuary. These locations have less happiness than other places and beside I could not have Danse in Sanctuary. BoS manage to sniff him out so they begin to attack the settlement. Beside, Danse often stuck inside of the premade houses. Tired of all that, I fastravel with him to Graygarden. Haven't seen any BoS there yet. There are no good reasons why players should send companions to default location again, just stash them in any settlement that suits

Cheers,

-Klevs