I'm not an expert when it comes to why a manufacturer "skips" a particular switch diameter-- but I suspect it's because O36 is NOT one of the original tubular diameters. Lionel only made O27, O31, O42 and O72(if i 1missed one please add it) switches. When Atlas deceided to make O gauge track, they went from O27 diameter to O108(with 9 inches between diameters) for track, but started switch diameters at O36. That's why we have so many discussions over this subject--- there are NO standards to Ogauge track except the 1.25" between the outside rails!