I'm not an old-timer, but in only a couple months of attempting to match UPs to MPs I've noticed it's rare to find a match. My theory is that there's a whole lot of foster youth that have aged out of foster care and are on their own. Because of their chaotic childhoods, they are more likely to be addicts, which makes them more likely to live a dangerous lifestyle.
I really wish more was done to free foster children for adoption, and I wish anything was done to prevent those with many children who have been lost to CPS to continue having children. My mother knew a woman who had 10 (!!!) children, none of which remained in her custody past the age of three. By the time her parental rights were taken away, the poor kids were almost, or already, teenage. So sad!
Of course all of these UPs aren't aged out foster youth, but I suspect at least 60-75% are.