I still think it's a leisure accessibility thing. The example from
@Helina reflects a different culture in Finland, and I'll wager we get that across the board. City versus country, different countries, different regions of the world and especially different generations. In Europe, people have more freedom to develop things like hobbies and interests, with generally better working conditions and leisure time than in a lot of North America. We get shorter vacation times, less flexible hours, etc. I'm kind of jealous when I talk to European aquarists about the old 'work/life balance' thing. They tend to have more time to really get into things.
I think the hobby is changing as society changes and women get more opportunities. When I look at photos of club conventions around the world, when you factor out the white haired crew, the young ones are much more likely to be women. I'll wager it'll be much more even in 25 years.
But now, in my regional experience (eastern Canada, Quebec and the northeast USA) there are a lot more old guys in the hobby than older women. Another big change I'm seeing is an increase in the local number of Asian and eastern European immigrant aquarists, with quite a few women taking the lead in the aquatic plant and aquascaping hobby, though they don't seem as represented in the 'contest' type scene. There are a number of couples around here selling plants online, where the guy is the face of it but discussion leads you to the woman, who really knows her stuff. The aquatic plant hobby seems to have a different dynamic, as does the shrimp scene. It makes sense, because both of those are new relative to the fish hobby.