I use my bikes foir transportation anytime I don't have to carry more than 40 pounds of weight, and if I have the time to reach my destination by bike.
I live in the Cohutta Wilderness area of N. Ga. at the foot of Grassy Mountain, in the Southern Appalachian Mountains. The pavement ends 1/4 mile past my house and is a Forest Service dirt road for the rest of the way through the mountains, until you come out on the other side at Blue Ridge, Ga......45 miles away. There are trout streams within walking distance of my house, but they are walk-in or bike-in only. It's all hiking and horse trails beyond my house. There is a convienience store a few miles away on US 411, and a small Post Office. The nearest towns with any real stores are Chatsworth, Ga. (8 miles away and few bigger stores), Dalton, Ga. (18 miles away, with a Wal-Mart), and Cleveland, Tn. (28 miles away, where my office is).
I ride my mountain bikes up the mountians to ride trails, hunt, fish and forage, using an INSTEP trailer to pull equipment, fish and harvested game in and out of the forest, as well as haul; firewood home, and garbage to the dump (4 miles away).
I use my Specialized Crossroads (fitness-type bike) for going to the grocery store, library, errands and short (< 20 miles) rides. I have it modified into a long-distance tour/utility bike.
I use Giant RS Road Bike to go to the office, club rides, centuries and touring (if there are no major mountains, otherwise I use the Crossroads).
I ride U.S. and State highways most of the time, as well as county roads. And I do some off-road riding, by necesity.
Semper Fi!