Yes I would say about 80% of most of the groups I've attended has been either singles or people coming without their partners. For a first workshop it often tends to be more couples but the social aspect of it naturally encourages mixing groups, especially because to do it safely you'll need one or two "spotters" that help keep you safe.
I live in Austria but I travel and have trained through most of Europe where it's similar. The international people that I've met have said it's similar in the US but I can't speak personally about it. I've been doing it for about four years did a teaching program last year and teach weekly classes now.
I've been into contact improvisation, some partner dances, and acro, and the scenes are structured by social circles that are much broader that most romantic relationships.
You become part of a scene by showing up regularly, practising, and occasionally making friends.
If some of these activities have sensual components (communication through touch, syncing together, sharing an understanding of the music…), there's no need to link that to romantic connections.