Why we used MPLS ?

mpls = multi protocol label switching as its name identifies , its a another method of traffic switching which relay on label rather than ip routes. 

the label generation and advertisment is done by another protocols. 

and the label switching process can be used to carry not just ip but many protocols , that's why its a very favorable choice as core switching protocol in isp network where isp has to carry many client's traffic over its core and give the clients a pure vpn network . 

Without MPLS technology Service providers need to maintain separate infrastructure for  Customer Routes(Private IP range) and Public Routes(Public IP range) .With the Help of MPLS L3 VPN technology,Service Providers are able to separate Customer Routes from Public Routes inside single infrastructure.

WITHOUT MPLS SERVICE PROVIDERS PROBLEM

1. Separation of  Customer's route to avoid overlapping of Private IP address.
2. Separation of Internet routes (Public IP) from the Customers Private IP address
3. Separate infrastructure for Customer Routes maintenance and Public Route maintenance 

The above problems are overcome by using MPLS technology.It has the following basic advantages

• Single Router is used for separating the customer routes with the help of Virtual Routing Table for each customer(MPLS VRF Virtual Route and Forwarding)
• With the help of MPLS VRF Global internet routes and Customer Private IP address routes are separated.
• With the help of MP-BGP  vpnv4 along with MPLS VRF only Provider Edge Router(PE) connecting Customers need to maintain customer routes.The intermediate routers (P-Router or Core Router)need not to maintain customer routes.
• Single Infrastructure to maintain Customer as well as Internet Routes.