the problem with bringing up children badly only comes out in the long term, far too long for any gov to worry about seriously - unless voters make an effort to judge them for it and let them know they think it's important.
these kids will grow up and they environment will shape them and their behaviour in turn affects us all. That's why it's a worthy tax spend for everyone, even the completely selfish.
same goes for many or social and environemntal issues. the 1 % GST saving could be better spent on a whole range of policies, that would ultimately yield a cost saving - less social workers, police, environmental damage, recovery, pollution related illnesses and so on…it's fine to think with your wallet, but don't be stupid about it, look at the long term