In addition to what others have said, the serious answer is that if we provided actual social supports for single parents, low-income people, people with substance abuse and mental health issues, etc. then our adoption rate would probably be significantly lower. Many people who give up their infants for adoption willingly do so for financial reasons, which is really fucked up. If we actually prioritized keeping those families together, we could do it; you see other countries with extremely low adoption rates that have those kinds of policies.

Obviously sometimes children will still have to be removed for their own safety, and in those cases adoption is the best option should the issues be so severe that reunification is impossible. But there are a lot of adopted kids who probably could have been raised by capable and willing birth parents, at least in the US.