WannaBe I can only speak for myself. But I went into a second older child adoption, having dealt with serious issues in the first adoption, so I was definitely not unaware. I suppose because a) despite serious difficulties at points, we had come to a point where we loved each other and things were going really well and we were a proper family unit. I knew that it was a loving parent that had made such an enormous difference in her life - so I wanted to do it again, and b) I never wanted an only child. I was still in my 30's with a nearly adult child, I was definitely not ready to stop parenting yet. I had years left in me and I knew it. I don't believe that older children should be denied a permanent family because of their age alone, if they will manage and attach within a family. I can't imagine my children alone in care with no one who wants to weather their challenges with them.
I also know that I would have been miserable as a childless woman. And I know other parents who despite challenges, are ultimately much more fulfilled as parents to a child who has challenges, than childless.
The majority of adoptions don't break down, and we all go into adoption with hope, hope for the best scenario, hope in the face of the unknown. Yes, I think we downplay the difficulties to ourselves...SW's can certainly downplay it...but otherwise perhaps facing childlessness or a very limited family size...you can't face the idea of this not working out. I know families who adopted older children and they have few difficulties which is amazing and fantastic for them.
But really, other parents would not have adopted again in my position. It depends...some of us are just willing and find we are comfortable with choosing more intense parenting and behavioural challenges. Other people are not comfortable with doing that, and that's okay. I know if i had my time over, I'd do it again. But if I had my time again, I'd do a lot more preparation and seriously adjust my expectations, which still come to bash me on the head sometimes.
I think realistic preparation for adoption is crucial. If families want to go ahead, we then need to seriously invest in support. Lack of support is a major factor in many disruptions.