'The whiff of dynasty builders'

It's the same lament every year, usually from the losers, that "you don't learn anything from the Community Shield season opener". This time however, it was Arsenal and Man City, clearly the two favourites for this season's Premier League title. If, as it is often proposed, the Community Shield is little more than a glorified friendly, why did both Mikel Arteta and Enzo Maresca field just about the strongest sides they could muster?