For the last time, that simply isn't an accurate portrayal of the situation. The "opt out" procedure isn't the same as simply saying no. It burdens parents with the requirement of applying by affadavit to be listed as a "conscientious objector" pending government approval.
And even if you don't consider that process excessive, there is also a long track record in this country of busybody liberal bureacrats at Child Services using "conscientious objector" applications as evidence to snatch kids into foster care. There are also left wing busybody legislators who file bills every year trying to change the "opt out" form from a one time thing to an annual process that must be completed over and over and over again.
And that'll simply fall under the child abuse label, or negligence (in providing for the child's health, according to some), or endangering the welfare of a child. There's lots of ways social services can get you. If someone doesn't believe it, they can talk to or read up on all the homeschool pioneers who had their kids put in foster care with those charges, for simply homeschooling their children. Social services has done it for less.