When you have no receiving threats, your passing game is playing uphill. The defense is free to blitz and disguise coverages because they have nothing to worry about in the secondary. You're not gonna see creative blitzes against a team with Dez Bryant or the like, unless you also want to see a TD. It makes playing QB a lot harder. You can look at the great QBs around the league and not see INTs like the one against Pittsburgh, but you also won't see them play coverages like that.