What is there really to comment on? The stock rear tire seems to be good enough for most people. Those who want a street tire have choices, and those who want more traction use ATV tires and work around the fact that those tires weren't designed for this rim (these challenges appear to be minor obstacles for anyone with any mechanical or problem solving acumen).
The stock rear tire fails when it is used in a manner not consistent with the overall design of the bike: it is not meant to be a competitive racer through mud. The tire girth equates to relatively lower pressure per area on the surface, leading to the tire floating rather than digging in. Under most circumstances this is fine: riders who want to tread lightly are able to do so without leaving ruts. Going over sand and loose dirt without making a huge rooster tail is easy. But screaming through mud and obstacles is simply not going to happen. This is why motocross racers still use skinny tires: those tires are simply better for that task.