this happens to me if i am not really 'there' mentally. if i actively try to be a part of the group, i get my fair share of attention, but i have to 'show' that i want that, if i disconnect, i get left alone.
this was a great realisation on my part, and something i have trained on, as actively disconnecting can make me pretty much invisible; a great skill to have if you just want to be left alone when going from A to B, this state also allows me to pass trough dense crowds with minimal touching, for some reason people will step aside from me without looking or talking to me.
i have had friends of mine comment at that, they started just behind me "you are tall, you make a path", yet the people i move past will step back into place as soon as i pass, needing the next person in line to make his own path. more often then not, i have to wait for the rest of the group to catch up to me, almost as if i move trough the people itself like a ghost.