Sweet Thing asked me about this, she has never had an interest in gun until she met me. I guess it would be best to describe her as curious about them since I have such an active interest in them.
My in short form answer was that full auto stuff is a rich man's toy. You have to be able to afford one, last time I checked was when Mac 10s (cheapest point of entry into automatic firearms) were $3000 or so + the tax stamp. Then the next problem is keeping said firearm fed. It is quite fun giving a recalcitrant target a couple bursts or more. In basic training you couldn't have beat the grin off my face after I got to play with a M249.
Long form answer, and I have given bits and pieces to her already, I see no reason for the 1934 National Firearms Act to exist. The politicians at the time played semantics by claiming "It's not a ban, it's a tax." It only serves to burden law abiding citizens. Just ask the Mexican cartels how hard it is to obtain their equipment due to draconian Mexican gun laws.