Probably is a matter of reputation. Unmarried singles from the opposite sex living under one roof.
that was my first thought as well. Charity comes in a distant 2nd or 3rd to the reputation of the Organization. If any charity or good deeds can bring into even the slightest question as to some untoward conduct, then it's best to avoid.
So, for argument sake, let's say the pioneers leave this couple's home. They both find apartments elsewhere. Just so happens those apartments are in the same building. An old Victorian home turned into 4 or 5 apartments. What then? They're still 'technically' under the same roof, though in separate 'rooms'. No real difference than bunking in the couples home - is it? Where's the line of difference?