I'm going to guess, and it's really just a guess, that Market Force did not make their site slow so that shoppers would not be able to perform as many shops.
I also wouldn't say that saying MF doesn't want full time shoppers would be an exactly true statement. I believe their shops are very easy, so they do not see the need to pay more for better quality reports. I don't think they dislike full time shoppers, just between full time and part time shoppers they have no preference.
There are reasons that a body stays in motion
At the moment only demons come to mind