That's only because people choose to base it on looks. Some people choose doctors and lawyers based on looks when what really matters is, can they treat your problem.
You go for a massage based on how it feels, whether therapeutic or not. The looks is a bonus.
If you try to argue that point, think about this. If your therapist (or doctor etc.) is very good looking but the massage (or whatever service you are seeking) sucks, tell me that you would be thrilled with the experience.