Why do we go for ASP.Net MVC?

Question

My project is in ASP.Net webform and we have plan to move on ASP.Net MVC.
Also Microsoft is recommending to move on MVC. on google it I can see many feature but i am not satisfied to migrate it.

i have couple of question on migrating to MVC. Is there any points you can strongly enforce to do migration?

Question:

  why do we go for MVC?
  Is there any strong reason you can say because of this you should go for MVC?
  Is there anything we could not achieve in asp.net?
  Is there any metrics will be improved in aspect of performance, response time?

Thanks
jai