It benefits the organization for its adherents to be different without just or reasonable cause.
Birthdays, Thanksgiving day, Mother's day, etc.....there is no biblical reason whatsoever to avoid these celebrations, while simultaneously condoning anniversary celebrations, graduation parties, baby showers, etc.
But....it does serve as a litmus test to see how loyal you are to utterly stupid and pointless regulations.
If you are willing to overlook the hypocrisy of denouncing Mother's day due its "pagan origins" and "honor of a creature", yet are simultaneously willing to overlook the pagan origins of wedding rings and overlook the "honor of creatures" at a wedding anniversary party, all because simply "we say so", then you are "one of us".
Same reasoning with beards - are you willing to follow this completely arbitrary, irrational, and pointless unwritten mandate? Good, join the club, now you can have some "privileges".