These jobs are given to the lowest level techs, the poorest paid techs, who are often pressed to give "Express Service." Of course, this kind of thing is also endemic at quickie oil lube change places, since they even pay less, in many cases.

Over time, I noticed this, as well. A few years ago, I started changing my own oil. I'm sufficiently OCD to do it exactly right. 

It could also be that in their rush to get the oil change done quickly, they may not wait long enough to drain all the old oil out and then put in the commensurate number of quarts and Wala, you're now overfilled. It sucks, in most cases there's little incentive to the job right. I'd bet the oil change jobs have a high turn over rate. 

Thank you.  I have caught them doing this twice and make them pump out the overage. I am somewhat suspicious they what to brake my car so I will buy another one.