Because the essence of a treatment is “authority”. If we cannot heal on our own we appeal to a higher power over us, in whatever form seems appropriate, and by whomever it is administered. That is a house 10 matter.
Ideally we will have a L10 which is essentially dignified and in positive reception with L1; if it is accidentally strong all the better. But most situations are not ideal and we take what we can from what is available.