Adoption is not very much promoted in Islam.
I think its based on children growing up to be adult and not really 'Mahram' to parents. There is no value of "Munh Bola' Rishta in the religion. Someone need to check that. Also If I am correct, an actor from Hollywood married to his adopted daughter after his wife died.
Now adopting and helping unfortunate kids to be good citizens and growing up to be good people with resources can be done without actually bringing them up in your house or perhaps bringing them up to a certain age.
adoption is very much promoted in islam, what people get caught in is semantics..if you think of the islamic concept of adoption similar to fostercare there is no issue.
children can be mehram to parents, if they have been nursed, and they are mehrem to the 'parents' biological kids as well. IN the end we are not animals and one does not look at his or her adopted kid and say wow..lookin fine, come here and gimme some lovin'
There are issues in terms of inheritence, however there is nothing stopping the beneficiaries from gifting their sharaee inheritance to the 'adopted' kids.
while there is no munh bola rishta in islam, cousins are na mehram too, but that is something where many people dont observe any sort of hijab etc.
you are correct about one actor..woody allen marrying the girl he adopted, and I dont think it was after the wife died anyways. But using that one guy as an example is not very responsible.
and sorry to say, orphanages or such facilities do not compare to the home atmosphere.