I can reach some ATV and old logging trails with about 1/2 mile road ride. That's not too bad, except that half-mile is a really steep uphill that I hate to do from a cold start.
The nearest singletrack is about 15 miles one way. So indeed, I often drive 15 miles to ride 8.5 miles.
There is some really great singletrack an hour away. I do not usually make the drive unless I'm headed into town for some other reason. I am not usually one to drive for an hour just to ride the bike. Mostly, I ride closer to home. It's just my way.