I'm with Blackdiesel on this one. The only reason they sell in the numbers they do, is because they look like the real thing! And, they're cheap to purchase.
They're often sold with tag lines like "indoor practice when it is cold outside, or "they have the look and feel of the real thing". The truth is, even as a 10 yards, they're more like a shotgun than an airgun. They may have the look and feel, but they sure don't shoot like the real thing. Fact is, serious firearms instructors abhor them. And the little orange/red rings sometimes required? They're easy to remove—some even unscrew!
While air gunners can use any excuse they wish, they're typically not the ones buying the vast majority of these look alike weapons—it is nefarious thugs because they know common folk can't tell the difference. Just ask yourself the question.... What would you do when a thug comes in to rob you with a look alike pointed at you?