> it's kind of odd how nowadays everyone goes to the gym. Growing up as a late-stage millenial, gym goers were a niche subculture

Let's not make it a generalisation. The US and UK are big into the gym thing, not every country is. I remember seeing some data that ~25% of people in the UK (maybe a slice of population, eg 18-30yo, can't remember) were regular gym-goers against 8% in France.