(sorry for the worse than usual sloppy autocorrecting/spelling in previous post should read:)
“We would never eat from a restaurant, caterer, or food vendor that does not display a hechsher that we trust”
Why not? If you trusted the store owner why do you need someone else to tell you it’s kosher?
If r’ belsky z”l owned a restaurant you would only eat there if he paid the ou to certify it?
Camps and schools have a morah Horaah that pakens their shailos, If you find him releiable, why would you need some other hashgacha on top of that?