That and the fact that they are the King of the drain plug thread strippers
I once had an argument with someone at work who couldn't see the benifit of saving a few $ to do your own oil changes. I mentioned that I don't do it to save a few $ but to do the job correctly and give my car a full inspection - something that the quick lube places don't do. The guy at work argued with me saying "how can they possibley screw up an oil change". The next week he came into work complaining that the quick lube place overtightened the oil drain plug which striped the threads on the oil pan. Needless to say he didn't argue with me on this topic again.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles