Even the men don't get a lot of master's categories until you get to the national championship races (they do it by 5 year increments there, for both men and women).

Men usually get A/B's and C/D's or 1 combined masters field, depending on the race. The fields work similarly to the women's, where higher cat men at 45+ can race down a category (and they sometimes have D's, where any guy, any cat 50+ can race, but I don't think I've ever seen a separate D's field - even at the state races they race with the C's and are scored separately)