its is often found that certain types of people who may be on a social services watch list move house on a regular basis so that there children are not taken into care.
Or the social worker does not stay on that case long enough to monitor what is really going on.
For example the baby-P case.When the social worker came round to visit, the mother would hide the bruises on that little boys face with chocolate,
Also, social workers can be scared of the parents because they do become violent if anything is said against them concerning the care of the child or baby.