One of the considerations of choosing a WAN circuit is security, and the type of data that is being transmitted over that WAN link. If the data is very confidential, it should not be transmitted over public infrastructures, as it is vulnerable to be exploited.
MPLS VPNs were launched in early 2000, and even though it was highly secure from a transport perspective, a lot of organizations were skeptical about using the shared infrastructure of the SP for their internal IT environments. But they saw the huge benefits in cost savings with regard to building their own dedicated infrastructures using TDM links from SPs, and the availability benefits the users realized due to the redundant infrastructure of the MPLS SP. Also, the services could scale up and scale down by just changing the access port bandwidth of an Ethernet port, and thus made the networks...