I root my Android phones to remove all the bloatware. Since you are coming from iOS, you didn't have to deal with all the extra stuff carriers put on. I'm on Verizon and they load up the phone with a ton of stuff like their VCast applications, CityID, games and other stuff. And it can't be uninstalled. So I root to gain admin access and remove what I don't want.
Another reason I root is so I don't have to pay the 20 bucks a month to have a mobile hotspot or for tethering.
You can also do things like install custom ROMS.
I haven't had a need to root my Asus. I like plain vanilla Android, and happy with it the way it is.