Can't a guy sniff some glue in the privacy of his own home?

Today at Target I got some Loctite "Stik n Seal" indoor adhesive so I can fix a cap on a doorknob.  The girl at the counter asked me for my license.

"Excuse me?"

Checkout girl: "I just do what the register tells me and it says I have to scan your license."

So I hand her my Massachusetts license which has a kind of barcode on the back and now everybody knows that I bought some glue.  What kind of nonsense is this?  I can understand limits on cold capsules and pseudoephedrine but c'mon.  This isn't a component to make meth or some other dangerous substance but clearly a way to track "huffing" which - although dangerous - is unarguably a private activity.  The libertarian in me says that this is a slippery slope ending in the tracking cheeseburgers and Big Gulps.