Motivation has been the same for me since late 1980s BBSes days: the hope of chancing upon others who also could enjoy a bit of intelligent exchange for a season (if not longer).
And it's happened. But rarely. Still not sure if the infrequency says more about me or others. Or about plain 'ole dumb luck, given the primacy of "timing is everything" and "location, location, location" in this grand-ish unfolding of myriads of individuality instantiations.