Why leave steel path circuit after 1-2 objectives?

So I haven't done steel path circuit in a while due to incarnon farming burnout, but I've picked it back up this week. Every time I go into a public squad to do it the rest of the squad leaves after the first or second objective is met. You can't even rank up one tier with that. Is there something I'm missing because it seems the only reason to do sp circuit is for the incarnons/other rewards but if you're not even staying long enough to get one, what's the point even?