I don't see why, but Dish generally does not believe we know what we are doing and wants to have a tech do the install, making sure both tuners are connected, the right sats are being seen, etc.
I convinced Steve with executive resolutions that I did know what I was doing, and he succeeded (about a year ago) in Dish'n... Up two 612's for me at $25 shipping cost, each. 2 year commitment of course.
I had to have a tech come and install my 722 when it was swapped for the 3rd faulty 612 (which for some reason I was able to install the 2 612's and a 622 before by myself). I am guessing it is a shot at making $$ altho I didn't pay for my install as an existing customer with a crapped out box. ( Altho I DID find a $300 charge for a "damaged receiver" on my next bill! That was taken care of with one call, as the tech took it with him when he left, and it didn't have a scratch on it)