As was said, the advent of the PC!
Bairds was at one time the best place to look, but evne they have a much more watered down directory.
When I started a local I named BX, I knew there were no Nationals of that name. But I found out later there there were more locals with the same name. After affiliation, the point became moot.
The combonation of letters as BlueNYC2 said are huge.
Try Greekpages.com and see which beginning letters are most popular.