I don't think that closeness exists often ouside of T either. In T we have the opportunity to be completely vulnerable and exposed... the nature of the T relationship allows that. Our Ts have a commitment to us - to our wellbeing, to our healing, to our Selves - and we honor their commitment by paying them. We can entrust the heart of ourselves to them, because they have a commitment to be there with us to receive it.
In the real world? Anyone can walk away at any time. Ts are trained not to judge, friends and family are not. Ts don't have roles or needs that they need us to fulfil, but our friends and family do. Every other relationship in life is a two way street, but a T is there in that hour solely for us.
The same kind of one way relationship in the real world would probably be dysfunctional.