I'm not sure if the proper response is "ouch" or "screw them."

I don't understand some of these business models. Grainger here won't sell to an individual, but I've bought <$10 of goods from them using a corporate credit card (but I told them it was for work. Yes, to make my bike work.) My local Fastenal sold me a single allen wrench and half a dozen single bolts, but when I needed a replacement bolt out in Arizona, I had to buy a package. We used to have a wholesale screw and nut store in town; they'd sell me half a dozen grade 5 single bolts as long as I bought a box of some screws, so I bought a box of wood screws. How do those policies make sense?