“According to the National Hot Dog Sausage Council, the reason why isn’t as strange as you may think. The NHDSC—which was founded in 1994—explained the mismatch packaging is simply because of the way these things were sold back in the day. In fact, it wasn’t until 1940 that we actually began seeing hot dogs packaged in packs of 10 (which is why you typically see in stores now!). So why are buns not in 10-packs too? The NHDSC says it’s because of the way they are baked.
“Sandwich rolls, or hot dog buns, most often come eight to the pack because the buns are baked in clusters of four in pans designed to hold eight rolls,” said the council: “While baking pans now come in configurations that allow baking 10 and even 12 at a time, the eight-roll pan remains the most popular.””
https://www.yahoo.com/lifestyle/theres-actual-reason-why-hot-100000628.html