I'm an older "backpacker" turning 25 in a couple weeks. I've got a well paying job and I could afford to travel staying in hotels, hiring taxis, and renting cars but I make a conscious effort not to for several reasons. One, I like to travel alone so staying in a hostel allows me to meet other travelers. Also, being thrifty with my expenditures allows me to enjoy my experience for much longer than your typical tourist.
I disagree with the description of backpackers as a homogenous group of drunken stoners. While we do tend to meet up at hostels at night and head off to the pubs, in the morning most people will scatter like bugs into their individual directions. We aren't sitting poolside getting served drinks by the "locals" instead we are riding public transport and truly experiencing a culture.
I'm addicted to travel, and backpacking allows me to book a last minute fare, throw some junk in a bag, and head out the door worry-free. It's the only way to travel for me. I've met plenty of fellow backpackers/hostel dwellers well into much older adulthood. I'll probably be like that someday.