IEEE Please

I understand why there are age restrictions when buying certain products. Alcohol, cigarettes, and lottery tickets can be addictive and shouldn't be purchased by people who aren't able to fully comprehend the long term effects of them. I can even understand why certain over the counter medicines have age restrictions on them. I believe that I've heard that certain cold syrups are used in meth labs.
What I don't understand is why I was carded yesterday. I know I look like I'm 12, so when I buy restricted products, I know to have my license ready. I just deal with it. When I'm buying allergy medicine, I don't understand why I have to show my I.D. to the cashier.
I was in the U-Scan, purchasing a few things. Among them, glass cleaner and allergy medicine. Let's just take a moment to think this out rationally. About the worst thing that I can think of happening with allergy medicine is it gives me a dry throat. I'm not aware of any hallucinogenic side effects, drugging, or drug recipes that call for allergy medicine. Plus, if some poor underage person is in need of some allergy medicine and isn't old enough, what are they supposed to do? Wait around outside the store and ask someone to buy for them?
Glass cleaner is toxic if consumed, can be considered a weapon if you spray it in someone's eye, and has high concentrations of ammonium in it. Yet, I'm carded for my allergy medicine and not the glass cleaner. State laws can be so stupid sometimes.