Because even though I haven't read the specific rule dealing with this in some time I was under the impression that a runner cannot be 'aided' by any other offensive player.... which DOES bring up a huge 'gray' area in that they CAN block, and block a player in contact with the runner... meaning the distinction between 'aiding' and 'blocking' can be quite murky... but to be clear...
Using an exaggerated example... if any offensive player other the one in possession of the ball ran up and pushed from behind, intentionally aiding the RB... or anyone in possession of the ball... that would be illegal. No?
