Not only does this make life easier, not having to keep a part of your life secret, or to remember who knows how much about what, but a whole new range of people are aware what a naturist looks like out of uniform, can learn the difference between naturism and sex, can ask questions or be told what it's about. If everyone knows a hundred other people, the ten thousand BN members could spread the message through a decent fraction of the population directly, and with friends passing on the message to their friends, to most of the population.
And yet people don't. They are worried about being mocked. They are worried that they might have problems with their job. They seem to believe themselves that naturism ought to be something secret.