There is definitely a quick-fix mentality that is fostered by our over reliance on pharmaceutical drugs and our many "masking" treatments (such as pain relievers, etc.). And people often have a hard time sticking with anything due to the pace of modern living and the shear abundance of information, mis-information, options, etc. All you have to do is go to the gym today and then check back in by the end of February to see how many people have gone back to the same routine by then...
That said, I always tell my patients a time frame within which they should expect to feel significant improvement and it is usually 3-7 treatments. I make this very clear in the beginning and I find that as long as they feel noticeable improvement (even if it's marginal) within the first three treatments, they have enough motivation to see it through.
And, yes, the herbs can be difficult as well - 8 pills, 3 times a day, etc. This is done, of course, to avoid side effects and increase the level of influence in the body throughout the course of treatment. While somewhat inconvenient, once people have a response, they are generally fine with what needs to be done.
Acupuncture is a medicine that is often used as a last chance option for many, many people. While in reality it should be among the first modalities that people try before more evasive procedures. When people come as their last option however, I find that follow through on recommendations, treatment, herbs, etc. is often very good particularly when they get a good response from the initial treatments - or at the very least that they understand what we're trying to do and can conceptually grasp how it will help them. I spend, as I imagine most acupuncturists do, a fair amount of time with my patients initially describing aspects of Chinese Medicine and how it pertains to their condition. This, I find, is very helpful for them and personally I have very few people who do not continue with a course of treatment through to the resolution of their issues.