This may be a holdover from the effect of the blowouts of the mid-1980s, when the NFL noticed that people were turning off the game in the second half. Case in point: the first few “Bud Bowls” had a commercial in every quarter of the game, but then, one year, it changed to just one commercial, in the first quarter.
However, nobody is really worried about Super Bowl ratings - it’s the rest of the season that seems to be the problem. I wonder how much of this can be attributed to the league’s exclusivity deal with DirecTV for NFL Sunday Ticket.