"it's not fitness, it's life"
Even if it wasn't, most people are wearing headphones. Sustained conversation would be difficult.
For example, the alcohol, as brought into spotlight by 'Animats. It's rather well-known (if a little tough to admit for many people) that alcohol is the "social lubricant". The way it lowers inhibitions and "screens off" pent-up stress, helps people make connections, build and nurture friendships.
It's not the only way to do this, but it's a way that works, and scales well among and across social strata - a fact that's been recognized since time immemorial, and the millennia of culture built around drinking only reinforce its bonding effects.
Serious iron gyms are usually a lot more chatty than commercial / for everyone gyms.
None of them are like the pub though, the pub has no activity other than socialising, it's the entire point.
The other part of this is that a third places mixes people of different social strata, and you end up talking to them, getting a cross pollination of ideas.
A self selecting hobby group is not necessarily this.
A hackerspace may be more like this, or a community garden, but a competitive chess club? Probably no.
A gym? Cost, physical exertion immediately excludes a lot of society from participating.