An important element of it being fair for you to cut the deck in the middle of dealing, which your friends may not trust, is that you do so in ignorance of who it will help and who it will hinder. By cutting the deck, you have explicitly made and acted on a choice (it is far less obvious when you choose not to cut the deck, the default expected action), and this causes your friends to worry that the choice may have been optimized for interests other than their own.