All of the advertisements, articles, billboards, etc. feature a conventional looking white couple who are adopting or fostering a child of another race (usually of African or Asian descent). Why is this the standard look of adoption?

Why not show an African American couple with a caucasian baby? Or an Asian couple with an Hispanic child? Even the pics of gay adoptive couples are typically white…how about a photo of a gay black couple going to an orphanage in Russia to pick up their adoptee?