Yes, maybe some parents can be aloof enough to cope with strangers being so close to their children (I take it some have met only through the scheme) but I know for a fact I couldn't do that and ask some of those realted to you who have kids and they'll probably say the same.
It's stressful enough when those related to you interefere at times!!
You always appreciate their help, but being forced to LIVE with them?
One size never fits all and if it fits some then fair enough, but perhaps too it's early days for some of them:-)