I agree that these things might be necessary. Also I know that there are therapists who understand and accommodate those needs. They might be rare but I personally have met with two such therapists and I'm currently still seeing one of them.

Why many or most therapists don't understand it? I don't know. Maybe because most of their patients have been well enough not to need outside contact in such a way and this it has never occurred to them that there are patients who need it?

Also, most probably these therapists are afraid that their patients become "overly dependent" on them and thus it might feel safer for them to keep their patients at arms length. I would call it lack of experience and lack of personal therapy work (because understanding one's need to keep his patients at arm's length is perfect topic for someone's own therapy).

Anyway, I personally would not see such a therapist.