Bridgestone discontinued the RE-71R in late 2019, and unfortunately the replacement in Japan is not as quick so therefor Bridgestone of America decided not to bring the replacement to the US. Once that decision was made they ramped up production of the 71R in Japan prior to switching all the tooling and sent pretty much ALL of them to the US. Tire Rack got most of the supply, but since they are the largest retailer and sell the most tires their stock is currently lower. However I've heard they are getting more stock of some popular sizes soon...not sure if they are buying up inventory from other retailers or not, but I can assure you Bridgestone is no longer making the tire.
So, just know if you buy RE-71R's they will have 2018-2019 build dates on them, meaning they've been sitting in a warehouse quite a while. However, my testing says even older tires that are still new perform quite well. Most tests say the newer tires (Falken/Yokohama) are quicker than the RE-71R, but the Bridgestone is hard to beat for all around performance, durability, and feel.