When I was about 12, my friends and I decided we wanted to build a rocket, and one of us somehow had a formula for gunpowder or something like it. We found out we could buy the ingredients from a pharmacy, but when we asked the pharmacist, he refused to sell them them to us.
Then we discovered we could get rocket kits and ready-made engines from Estes Industries.
I learned to make a crude form of black powder when I was 10 or 11. You had to buy the ingredients in separate places, or at least at different times. Pharmacists usually aren’t stupid.
Remember the waterproof fuse you could buy from the ad in the back of Popular Mechanics? Good stuff.