You don't need to root your phone, it should perform as advertised without rooting! There are several advantages to rooting and several reasons why you may not want to.
Pros-
Run alternate ROMS and Kernels that can add functionality and features (main reason people root!)
Use apps that only run as root. Apps like Titanium backup, Adfree, ect.
Remove provider installed bloatware.
Cons-
Eliminates any warranty you may have.
May in extreme cases brick your phone.
Opens holes for malware. With total control comes responsibility.
I root/hack every device I own. It's habit and I feel that I'm only renting it until I can control it. Custom ROM flashing in particular can become habit forming.
With the endless search for just a little bit more speed or one more feature (that you probably will never use) one can often wind up with a device that's never fully set up or stable. It's risky fun that's not for everyone.
