I think it has to do with a lack of practicing. For years the extra point was just a formality. Now that the NFL backed kickers up blocking is a bigger issue. I know that some kickers have just flat out missed kicks but it seems that blocked kicks are on the rise. I think special team units need to work harder on blocking as athletes can jump higher and run faster so the kicking game has become something teams need to really focus in on.
I also think there is a mental aspect to these missed kicks. No kicker wants to be the guy that ends up costing his team a hard fought game because he misses an extra point, so I think the added yardage has made kickers think more than before.
It is exciting though, I personally think moving the extra point back was a great idea. Long gone are the days of an automatic point.