Why don't you believe it is the statutory duty when it is written in law 
You are not just advocating early adoption, your link makes no sense, it's as if you are saying that no-one should have a chance to parent based upon tick boxes ie a certain age, income, background etc.
When i said ask the DC, i am talking about grown ups that have come through the system, there aren't adoptive parents for everyone, you are proposing a massive change in the law. It is normally after the second or later DC that the families problems worsten, you are then removing siblings, it isn't as easy as you think.
A change in the law has come about after much research into a time when DC would be removed earlier and easier, it wasn't a good system. There are emotional needs to consider.
DC's that have an attachment to their parents suffer when removed, abuse doesn't start as early as you seem to think. There are women who have removal orders waiting as they give birth, it happens.
As a Local Authority Representative (SW) you strive to find a balance, it is happening at present.
DC's go on to recover from a less than perfect childhood with the right support without being removed.