It allows them to take advantage of mismatches

If they have Develin (a very good blocking fullback who can catch) in the game and the defense responds by bringing in big players, the Patriots can split him out and even empty the backfield and create a nightmare for the defense to cover (one of their RBs James White is an outstanding receiver; Edelman can't be covered by one person, nor can Gronkowski.) If the defense stays in a base or some other DB-heavy personnel grouping, the Patriots can run well because their o-line is good and Gronkowski is one of the better blocking tight ends I've ever seen.