Many of these healing methods were discovered and developed by very spiritual people all over the world. Some were part of various religions.
The methods have many similarities, and the ultimate goal is that the person being treated is helped to remove any negative or low-vibratory energy. Usually very spiritual people (not necessarily religious) want others to feel loved, whole and accepted. That is why spiritual, loving and compassionate people discovered and developed many of these healing methods over the centuries.
All belief systems should be respected. The healing is not about any religion. When you are being treated, you are in a safe, nurturing and respectful environment. It is all about you.