They have things like blogs, greeting cards, photo galleries, message boards, and newsletters etc. Many online bingo sites emphasize the socialization aspects of bingo through their community.
There are special games offered in the chat rooms so that players can communicate with one another while they are playing bingo. Players are encouraged to play in the chat rooms with special games and special promotions. These are features that you don't find in online casinos where many players just play their games. Some may use the chat room but many don't. There are no community aspects even mentioned in online casinos.
In many ways the online bingo communities are reminiscent of the community established in a church where bingo is a part of the situation. People know one another and make friends. They have a mechanism for announcements of news and events for the community.
These and many of the other social aspects of the church basement bingo are mimicked in online bingo sites because this is one of the things that people expect from bingo. These social aspects are what players associate with bingo. There is a bingo community whether it is online or land-based.