The problem with that is that we do not want giving birth to be an income method. We already have low class people having, more children to get more money from the state.
Poverty is not officially the reason for removal, more the side effects of poverty like malnurture, crime and too young mothers.
It doesn't make financial sense to have children, subsidies or not. At best the subsidies barely offset the cost. The reasons you mention make perfect sense.