It's the latest turn in the 'on-time arrivals' performance game. Airlines wanted higher on-time arrival stats, so they just scheduled the flights to take longer. Of course, if one airline pads their arrival times, and another airline doesn't, the airline doing the padding looks like it takes longer to get you where you're going. So, the obvious solution is to pad the scheduled arrival time, then advertise an estimated time of when they really think you'll land, but that won't hurt their on-time arrival stats if they miss it.

It'll be really fun when they start calculating minimum connection times on the estimated arrival instead of the scheduled one.