The reason .22 rimfire ammo isn't seen on shelves is some shooters (not all, but some) keep buying it whenever they see it, just as some (not all) shooters feel compelled to post on the Campfire anytime they find any in a store or on an Internet site for what they consider a "reasonable" price.
Distribution is also uneven. From what I've seen, most of the production goes to larger chain stores. When you place bigger orders, you get your orders filled first. These stores tend to be in populated areas, but they also have a very limited footprint in certain very densely populated regions, such as California. The result is that people living in small towns tend to have a hard time finding it, and people in the regions that gun-friendly big box stores don't bother servicing well are nearly SOL. As long as this situation persists, people will resort to going online, and that will keep the scalpers sucking it off the shelves where it's plentiful.
Smaller stores are also partly to blame. If I ever see 22LR in a non-big-box store, it's marked way the heck up to a price you'd only pay if you were truly desperate. They move minimal volume and can't get their next order filled in anything like a timely manner, so they still think it's scarce and keep their prices high, so it moves slowly.
