It's stereotype time!
My 50 plus years in the hobby, with a lot of conventions and such (it used to be a part time job) suggest that among hobbyists who are interested enough to attend events, the majority are male. There are areas of the hobby where women are the majority, with certain fish groups, for example.
The Cichlid hobby has always struck me as very male.
Killies (my niche) is the stereotyped older male, often really older.
The internet shows something different. The conventions tend to attract retired males, with leisure time, and males with money (to travel to conventions). People with kids or working class people only go to these things if they are local. Online, the scene is younger, and there are more women.
I sat outside a quality fish store on the weekend, waiting about half an hour for someone who for unknowable reasons had gone into a different shop. The aquarium place was busy. Most people going in were under 30 looking, and most were women. So that was a small sample, but interesting. Not only was I the only over 60 customer, but I was the only one with no tattoos.
