There are too many races, ethnicities, differently- abled, and unique people to group everyone into a specific month. If they don't have a month/day (whatever), then you're leaving them out... this is time-consuming and wasteful. The tape and flyers used to announce the celebratory gatherings is a big waste especially when email messages clog up our systems about the same thing. If you don't celebrate, you could be singled out as a bigot, if you do, you're just wasting government work time and eating more food, etc., using money that can be saved.
Respect everyone; don't just celebrate some.