If you're a self-built artist, the label could be using you for what you've already created. If you've got a huge fanbase already, millions of YouTube plays, and have cracked radio, a label deal can't offer you much more.
You have the potential to be shelved. If the label doesn't think you've got what it takes, they have the option to do nothing for you. Not to mention, your deal prevents you from doing much without them or their approval.