Holding is rarely called in the SB, been that way for some time. Lots of things aren't called in this game.
For whatever reason the NFL has deemed that penalties shouldn't be called in the biggest game of the year. We've all seen games that were complete eyesores due to the number of flags thrown. The NFL doesn't want people, who normally don't watch football, witnessing a disjointed game. They also have to keep the game on time, and having flags all game gets that out of whack. Imagine one of those long Sunday afternoon games, due to flags being tossed around all afternoon, happening in this game. It wouldn't end until 8pm/11pm.
The NFL is big business, the game itself with regards to competition is not what they are concerned about. Its a Billionaire's club, and they care about money.
Sure we have great players and the game, at times, can be a great spectacle. But the NFL is about churning out millions for the owners. The game itself, who wins or loses, is secondary.
No other sport is like this, where the rules are secondary in the biggest game of the year. Sure, whistles are a bit tighter in Gm 7 of an NBA or NHL game. But stuff still gets called. In the NFL they don't call anything.
Holding, pick plays, illegal contact, do whatever you want.
Not taking anything away from Philadelphia, they deserved that game. But for the true NFL fan, not the ones that show up once a year, it can be frustrating to watch.