I think that there is a misconception about what "rooting" a phone acutally does. Think of it as changing from a standard user password account on a computer to an admin account that has full read/write access. This is what "rooting" a phone actually does. It simply allows the user to have "Super User" or SU access to the phone. After you root a phone, it will not run any faster, or anything else after you just perform the root procedure. You simply now will have the ability to change files and permissions that you where locked out of before. Much like with any computer, there are several files that should not be changed and where locked for a reason.
So long story short, rooting is not a magical experience that will totally transform your phone. Rooting is the door that must be opened to make these changes.