The point is to travel by bike with camping gear. It's not about shredding black diamond downhill or whatever the trendy mountain bike thing this week is. Bike touring — bikepacking is really bike touring — is much older than recreational mountain biking and both are equally practical and impractical.
For example, this past summer I rode a 1,200-mile section of the Great Divide Mountain Bike Route from Whitefish, MT to Steamboat Springs, CO (single speed, naturally). It would be impossible to drive to every campsite, even if I had a car. For me it was visiting places, talking to people, stopping for pictures (I carried a Leica M4 film camera) amid a constant feeling of being in the moment. It was glorious.