When digital was first being pushed they claimed prices would be lower, that's not the case when a game has been out for a while you can usually get it far cheaper physically in a shop because shops want to clear out their inventory. It's more about controlling prices and killing the second hand market, I would say it's anti-consumer.
Yeah, I suspect another part of it is Sony/MS/etc don't want to upset online/high Street retailers who sell their consoles/games by competing and undercutting them with their own digital store.
The problem with that is it's resulted in IMO ridiculously overpriced digital copies of games. The fact I can buy something like demon's souls on disc via an online retailer for £60 whereas the Sony store charge £70 for the digital copy is ludicrous. Clearly the digital should be cheaper but for political reasons Sony won't sell it for less than RRP!