I did yoga from 1–3 times a week for several years. Both my wife and I quit when the classes were filled more and more with the spirtual/philosophical/pseudo-scientific parts of yoga, and less actual exercise… if I wanted to hear some version of the sort of advice you can get out of a mass-market self-help book, or some implausible explanation of how yoga can improve my life… well, I don’t need to actually pay for that.
We enjoyed the exercises and teaching method for the style of yoga we were taking (Iyengar yoga), but less thrilled with the baggage the Iyengar Institute apparently requires instructors to attach to it.
In addition, I have EXTREMELY short hamstrings (as in, despite being lean and trim, I’ve never been able to come closer to touching my toes than 4") and even though my instructor was patient with me, it certainly becomes frustrating to not be able to do half the exercises in any given class in a form that even vaguely resembles the proper form. (When you can’t even sit straight upright at a 90-degree angle with no back-rest, a huge portion of yoga becomes problematic.)