Depends, there are lots of reasons to root. Depends on your device.
I didn't see you post what device you are running so its hard to say.
If your device maker and carrier has loaded up a lot of non-removable bloatware, then thats one good reason. If there are tons of custom mods and ROMS (customized versions of android) you want to play with then thats another good reason to root. If you want to tether your computers for internet without any additional charges, thats another good reason. If you want to do full backups and restores of all your apps, settings and ROM, thats another good reason. If you want to overclock your device for better performance, thats another good reason.
I usually recommend that people use their device as stock for 6mo or so, just to become accustomed to it, research what is available for the device and have a baseline for its performance. Then consider rooting and modding.
Keep in mind, rooting WILL void your warrantee. However, most robust rooting solutions have a method to roll back to stock if ever you need to return the device for warrantee service.
Also, yes it is possible to "brick" your device while modding/rooting/flashing new roms or kernels. But even in that case there are recovery options, and if the device is truly bricked, even the carrier wont be able to tell it was rooted, since at that point it just simply wont respond to anything even the carriers can throw at it.
I've been flashing firmware to various devices for over 10 years now. Smartphones, routers, optical drives, flash drives, satellite recievers, modded computer BIOS systems, stereo systems, even TV's! Making devices of all sorts do things they were not originally intended to do and have only truly "bricked" one device. It was then RMA'd for a full replacement, no problem.
Just do your research and read, read, read!
But truly, most of the time for a popular smartphone, its not so scary.
What android device are you using and what cell carrier? I'd be happy to point anyone in the right direction.
*EDIT* Full disclosure. I unbricked an iPhone for a client today that the Apple Store "Geniuses" across the street couldn't budge, hence my longwinded post. I usually don't work on apple crap since their premium prices and smugness annoy the hell out of me. Apple and their customers can go have thier smugfest in thier spendy little hipster enclave. But this old hacker just bested them on thier own hardware, and that was the first time I'd ever even held an iPhone 4G. /RANT off.