From what I have seen on mine and many others, the factory ones are perfectly fine for
normal everyday uses, and should last about as long as the vehicle they are installed on, assuming they aren't abused or used for something other than what they were designed for....
However, if you have a special need that they won't work for, then I don't know of any reason you couldn't replace them with something better
Tires are another story though...
OEM tires nay not be the best looking ones out there, but are generally good for about 35-50k miles from new, depending on your driving, maintenance habits and the condition of the suspension system as a whole. But they are a normal replacement item that incurs significant wear & tear during use, which will affect the ride, handling and safety of you & the vehicle.
So in that regard, there are many reasons to consider aftermarket tires, be it for the above reasons or for mechanical/technical reasons (lifted/lowered suspensions/off-road/mud/sand/snow use) or just sheer appearance changes...