Do you like driving a car with a tiller and no seats? That's what it's like going from a real Linux installation to the kernel Google gives us. I want to be able to get to any file anywhere on my phone - maybe just to see it, maybe to modify it, maybe to delete it. If you look in /data, you'll see an empty folder. It's not, it has a lot of folders in it, but they're only visible (let alone accessible) to superuser (which is what rooting gives you - the ability to "be" superuser).
Running an unrooted phone feels, to someone who uses Linux, like being severely crippled. I usually root my phones as a matter of course, the same way I check the gas, oil and tire pressures in my car before a long drive. Not because I know I'll need it, but the car should have a full tank, enough oil to reach the fill line and proper pressure in the tires. And Linux should have su as one of its commands.
There's a reason Google doesn't include rooting in Android, though. Typing
su
rm -r -f /*
in a terminal app will reduce your phone to a box of useless hardware with recovery and download partitions. It's why Walmart doesn't sell dynamite.