Thanks! We are having an argument at work, and I agree that the apostrophe looks dumb.
But there’s more dissension on the issue than you would think! The New York Times is not consistent; it sometimes uses “for convenience’ sake” and sometimes “convenience’s sake.” The New Yorker uses “for convenience’s sake” except when they are quoting Virginia Woolf. Older editions of the Chicago Manual of Style apparently specifically reference “for convenience’ sake” but new editions drop the example altogether (but do include “for goodness’ sake” but also “for appearance’s sake”).
Anyway, it’s a dumb argument but a bunch of us were stuck in a conference room waiting for someone, and doing some group editing.