Anytime you have a very exclusive group - you must keep them bunched up and tightly huddled or you get diversity.
The JW religion was formed at a time when they branded themselves as the "answer" to all the "problems" other religions had.
Thus, no holidays, no cross, special name for God, neutrality, etc. This made them seem much more "otherworldly" and Jesus like and as though they alone were the keepers of a higher standard.
That has an appeal to certain people. The "we are Gods chosen people" rhetoric starts at birth and most JWs firmly believe it. They have disdain for and pity and even a form of "love" for the unwashed masses that exist outside of their exclusivity.
They don't mind if you join, in fact, they actively proselytize, The exclusivesness is not determined by numbers but by everyone adhering to the tight rigid path.
To leave is similar to going AWOL from the Army.