Some of the people involved writing various parts of the WSFS Constitution aren't around anymore to ask why they're written the way they're writter. Other people are still around. The WSFS Constitution, though, started off as a document for a gathering a lot smaller and less complicated than modern Worldcons, with a more homogeneous population. Also, the speed and accuracy of contemporary telecommunications, of sending electronic identical copies around to thousands of people in a short timeframe, didn't exist until relatively recently. Compare e.g. the current incarnation of Ansible to something run off a hektograph (spelling) and send around getting chewed up the the mail delivery system and received in Australia months later by slow ship...

And then there were those lyrics by Barry Gold (I think they were his).

"The song of fandom's a sad song...
"No cons... for the next ten weeks!"...

These days there can be more than six just on the same weekend, forget about gaps of months!