Well, not really. There are many reasons why people don't group.
In my case, I'm fortunate to have friends and family that call me on the phone often. And a really nice husband. The last thing I would ever want to do is tell my 87-year-old Mom "Sorry Mom, can't talk. I'm in a group." Or tell my husband "Oh, you made fresh coffee? I'll have some later. I'm in a group."
When I'm soloing I can just stop where I am, even if it's in the middle of a battle. If I die, I die. No big deal. I just don't think it's fair for me to join a group or team, knowing that at any moment I might I have to leave the group with no notice at all.
As far as being interactive with others, there are plenty of ways to interact with people without grouping. Answer questions in General chat. Buy/sell crafted items or mats on the GTN. Help out newbies here and there. And so on.
If grouping was a necessity, or even absolutely expected, I just wouldn't be able to play this game.