I'm not a psych major and I've never taken any human behaviour courses, but from what I've experienced in my 29 years, is that we all want to feel that sense of belonging. We are social creatures and identify with other similarly minded folks. In the past the survival of a our ancestors depended on fellowship and community. The phrases "it take a village to raise a child". What does it mean to us today? Not much, because we can just go on the internet, phone mom, read a book and get the answers.
It wasn't like that in the past, because people needed to take care of their basic needs (building shelters, making food and clothing), everything was a process involving hard labour and work. Therefore it made sense for "elder's and older siblings to watch the children", men to work "labour intensive jobs" and women to ban together to make food and clothing (among other stuff). I'm not getting to any "feminist or anti feminist point - I don't even really know what those words mean. What I want to get across is that historically and throughout antiquity in order to survive we needed each other.
What has changed? Well we are less focused on self preservation and more focused on self promotion. We can do things on our own, therefore we do! Reasons like the industrial revolution and access to resources on a day to day basis have made survival no longer a threat. But our need to belong is still there.
How many groups are you apart of? Groups or communities, meaning face to face contact! I like to believe that I feel 'safe' with my groups, "they have my back!" The need to belong is instinctual. So why resist it, join a church group, a mommy group, a fitness gym (that they know your name), a recreational activity, book club...sheesh anything! It's good for you! (I'm just saying-)