How can ISP's only do this now?

Most telephony networks are far more advanced than most people relaize. Even the older networks in your neighborhood can do more than you know. Networking is usually handed out in tiered service levels, and this is a way of locking in customers at different price ranges, as well as a method of alloting bandwitth and optimizing the network. When they want to increase profits and jump customers to a new level, a new tier is offered.