Just Wondering Why???

This is not a big deal, but why do you have to not only ground the dish installed on a building, but also run the coax downlead thru a grounding block when  at the same time, if you use a portable satellite dish for tailgating or camping, no grounds are used at all?  Isn't  the ground thru the 110v outlet, passed on thru the receiver, coax and on to the antenna via the coax shield?