A lot of places do, but they sell them in bulk. Most of us buy from Rex Grigg cause he's one of the few people that sell less than 50 lbs at a time. I could buy everything I buy from Rex locally, but it's only a little bit more expenisve(including shipping) to buy it from Rex and then I don't have to have 4 50 pound bags of fertilizer sitting around my apartment. At the rate which we use dry ferts, it would take FOREVER to use those 50 pound bags.
I ordered 4 products from him, 1 pound of each, that's 4 pounds. To buy locally, I'd have to buy 200 pounds worth of product. The 4 pounds I bought from Rex will last me a year. So, if I bought the 50 pound bags, they would last me for 50 years.