And until we can tie cognition, emotions and behavior more tightly to physiological brain function, it's going to stay that way. In the meantime, I believe clinicians adopt a treatment modality that fits with their own experiences and world view. Since we use ourselves as tools, there is never going to be a one size fits all model. I like Murray Bowen because his model jives with my belief system.
All in all, though, I dont think it matters what approach a therapist uses. The most important thing is to start where the client is, work to develop trust, and motivate the client to move towards change. If a client doesnt like me, I'm not going to have much success with that person. Fortunately, I'm pretty likable, but once in a while I'll see someone who I just dont click with, no matter how hard I try. If that happens I usually recommend a different course of treatment with a different provider.