I have only had ONLY 1 person that I felt was hooking me on purpose...Everything that hit a line....even drop shots, he called out. After the match, he told me that he called them that way because he though I was hooking him....weird....all perception. I filed a grievance to no avail. If I am not 100% sure that a ball is out, I play it....PERIOD! When I am serving, about half of the balls I serve that I see 2-6 inches out are not called out. I TRULY believe that 99.9% of the people are honest with calls. The ones that I think missed calls, truly beleive that they made the right call.
Sometimes people have no clue...they have not been properly calibrated. With that I mean that, at practice, whenever there is a close call, we all talk about it and make sure that we are all in agreement. sometimes we find that 1 guy might have been miscalibrated by 2-3 inches....It happens. But it's all good.