In reply to Mob.

It doesn't work like this. Labels are in touch with retailers. If you aren't on a big label, your album won't be on the shelves. If your album isn't on the shelves, people can't buy it.
Albums leak because of the retailers. Actually, not because of the retailers themselves, but their employees. When a label ships a new album to a retailer, they do this a week before its official release so it will be widely available. An employee of that store can get an copy and leak it. Some stores sell the album before the official release.
If the label release it on iTunes right after it leaks, they could really damage its first week sales and promo.