One reason it is good is that physical therapists are not technicians. Going to a PT is not like going to the mechanic with your car. When brakes go bad, there are only a certain number of problems and therefore only a certain number of solutions. On the other hand shoulder pain, for example, can be a result of many many things and there are many solutions to each problem. The physical therapists job is to find a solution that 1) is appropriate for the problem 2) appropriate for the person with the problem, and 3) is appropriate for the therapists expertise. As I've mentioned before, physical therapy requires a thoughtul evaluation process. This allows us to use our individual strengths to your advantage.
This variation is fine as long as 1) it makes sense WHY the therapist is using the treatment, 2) the therapist has the consent of the patient to proceed, and 3) the therapist is not treating in a way proven to be ineffective or unsafe.
This leads into many of the bad reasons for variety of treatments. And for this post I'll discuss the 1st: WHY the therapist is using the treatment.
The most common bad difference among therapists, and indeed all practitioners, and their treatments is why they are using them. You might go to one therapist and be told that your alignment is off and that is why you hurt. Another therapist might tell you that your fascia is restricted, and that is why you hurt. Yet a third might say that your muscles are tight, and that is why you hurt. Each one will treat you differently based on their reasoning for treatment. This is not good. There are many many outdated, disproven, and flat out bad theories running around out there.
When it comes to pain, any theory that is not up to date in pain science is questionable. There has been an astounding degree of advancement in this area and much is now known.
So, how can you, as a patient, know when you've been given a poor reason for treatment? This is unfortunately not easy. There is so much mis-information and opportunistic marketing out there that it's often hard to know who to believe.
The skeptical community can be quite helpful in this regard. I'd recommend looking at a few of the skeptic resources and searching for information. A couple that I'd recommend would be:
Science Based Medicine
You might be surprised at what you find out.
Expect qualtiy reasoning from your practitioners. That is a very fair expectation on your part.