Why does anyone need to ban RPGs?

Given that there are no cases of RPGs actually being used against police officers, why are they banned?

Now this may seem strange, but the same logic is at work in a recent gun right's opposition to the ATF's proposal to ban certain armor-piercing bullets:

"This appears to be a solution to a problem that doesn't exist," said David Workman, the Second Amendment Foundation's communications director. "I can't find -- nor can anybody else find -- any evidence that any of these bullets has ever been fired from a handgun that's harmed a police officer."