probably because he gets higher paying customers that way. he said earlier he gets priests and politicians who hire him because they think he won't know who they are.
Just think people would trust y more when they know y cant see so y cant betray them of expose sth(for example here: that they enjoy his "massage") in that way he gets more rich and popular clients so more money while reassuring that he cant expose their image
It is morbid and hot... Just the way I like it. Can you guys also help me why the baby boy uke is pretending to be blind?