Why are most of the communities so... Empty?

For most communities, especially some of the smaller ones, have posts that are only as recent as 2 months ago at best. I noticed that there is frequent activity on The big communities such as "chapotraphouse", "chat" and "news"... but that same frequency of activity isn't replicated on most of the other communities.

For communities like "movies and tv shows", it feels like visiting a ghost town.

Is activity for people here mostly off this site and elsewhere? Did I not get an invitation or something? It feels like, with regards to activities such as playing games or watching a movie, I see no signs of people on this site doing anything.

So why are most communities lacking in activity?