Square dancing is to strengthen the body, to delight their spiritual life. Wearing a mask to dance is unnecessary if it is not necessary for the dance. If it does, it is some 'celebrities,' who want to show off their dance moves, but are afraid that people who know them well will recognize them and laugh at them. But again, the lure of dance is so great that wearing a mask is not a bad idea. This belongs to the dancers themselves.
The onlookers can enjoy the show if they feel it's good; if they don't feel it's good enough, they can turn it off.