Addiction is so complex, especially with the luxuries around Peaches that enabled her to be an addict, mainly safely.
From SS perspective it is such a high threshold to meet for there to be an intervention, not every drug abuser will have their children removed. I saw earlier in the thread about the babies being born addicted. There are lots of ways they will manage an addicts pregnancy, again even more so with the access to service and money Peaches would have had. An addicted baby is inconsolable, hospitals/SS have special staff sometimes called huggers to help them through the withdrawal. Heartbreaking.
And as for Tom, he was in an incredibly difficult position, where yes you would and should always put the children and their well-being first. Sadly when you are dealing with a addict who you love it can get extremely complicated.