Because you can pee outside without people looking at you funny.
Because you can see stars you don't see in civilization.
Because you can go several days without bathing and that's ok.
Because there are things that are inedible at home that taste divine outdoors. (We learned that about Dinty Moore the hard way. Ugh)
Because you can abandon everything that you can't carry on your back or on your pack animal (if you have one) and live simply.
After 9 days in the back country with NOLS, I came back, took a looooovely shower, and I totally would have gone right back out again, if I could have.
I need to camp more often.