TBH those sizes are only used by the metric fasteners in the USA or by non standard fasteners. Ironically the USA metric fasteners are based on the international ISO standard, but most of the world relies either on the DIN german standard which is 13mm for m8, 17mm for M10 and 19mm for M12 (anything from Europe) or for Asia the JIS which is 12mm for M8, 14mm for M10 and 17mm for M12 (for flanged style fasteners but if they use a non-flanged fastener they also use DIN sizes).
I assume the sizes in the USA are such to allow more compatibility with SAE imperial tools? Just sad that it includes so much more sizes for no good reason. If things were more unified we'd need 4 wrenches for the most common fastener sizes (M6, M8, M10 and M12), but instead we need 10 of them to have the right one for every standard.