I think that a lot of it has to do with people underestimating its potency, as well as that the drug is in you 24/7 so your body gets really used to operating with the suboxone in it. A lot of people expect their tolerance to go down while on suboxone, but soon find themselves in over their head, depending on their dosage and previous usage of course.
I know that for me I got on suboxone to make treatment court a hell of a lot easier, but since I was already being drug tested once a week I would get high right after the test, the next two days, then stop until after the next test the following week. I was getting high as can be from sniffing 4 bags of dope, but even on the other days I didn't do that much since I couldn't afford it. So when I went to the doctor and he put me on 16mg/day not only was I using 4 days more a week, but it was a steady dose that was as potent as the highest dosage of heroin or oxy I was using at the time.
So after 18 months of that it was no wonder my receptors were shot, and it took forever for them to get back to normal. 4 years later and I still have the same tolerance that I did right before I got on suboxone, but that's only because I never went above 4 bags, and usually do that once a week and sniff a bag or two every other day to stay well.