I agree with John Battles. In the flick, all the bands make it clear that they are fully committed to their bands and won't be stopping anytime soon. They all make it clear that it has been a lot of work and they don't expect to make it big. All the bands express they enjoy what they do, but agree it is constantly challenging and gratifying at the same time.
Striking it big time like The White Stripes is a one in a million shot. I love The White Stripes, but it still boggles my mind that they blew up the way they did, considering there are so many other similar and great bands out there that hardly "made it big" from that White Stripes explosion. Another reason I think it is amazing to me that The White Stripes got as big as they did: I would wager that the first three White Stripes records (being quite fuzzy/raggety garage) were very challenging for the masses, considering people tend to like slick and radio-ready stuff more along the lines of Strokes and other more "commercialized" bands.
Side note: I also saw The Cynics when they toured a couple years back (they played Ann Arbor) and they performed to only about 40 people at that show, too. It was an amazing bill which included The Sights and The Hentchmen, from the nearby early 2000's neo-garage explosion "hotbed" of Detroit. It was a great show chock full of legit garage acts, but it was sadly under-attended.