Via BBTF, Maury Brown shows that interleague games bring in the same fans as intraleague games:

The problem has always been that interleague occurred in two short series, first in May that surrounded Memorial Day and later in the season when a longer stretch is played in July. The limited number of games, one of which took advantage of the 3-day weekend, and the others around summer when weather is at its best and kids are out of school, never really spoke wholly to how popular interleague might be over a long stretch.

Now we have a long stretch:

While the rest of the season is yet to be played, the numbers compellingly show that interleague is not as popular as the past numbers have been said to be. It’s not that the “rivalries” aren’t popular, they are (they averaged 30,876 across the Rivalry Week in May this year), but rather balanced interleague throughout the season pulls in pretty much the same crowds as traditional interleague has.

So MLB stacked the deck to make interleague play look good. That’s not a surprise, given that a used car salesman runs the game.