You know, people don't always do what's best for them.
They make decisions and select choices on the basis on many reasons, and 'what's best for me/my baby?' might or might not be part of it.
How can buying cot bumpers because they look nice (FFS) while knowing their (un)safety record be a decision based on 'what's best'? How can smoking when there are babies and young children around be doing 'what's best' for anyone?
There are limits to how far parents can be compelled to do 'what's best' and in some cases (use of safety restraints in cars, for instance) laws have been made which actually do exercise compulsion, and rightly so, IMO. Same goes for inappropriate punishments - our society has made it illegal for children to be physically punished beyond a certain limit. I am quite sure some parents think it's 'best' to batter children with sticks as part of ordinary discipline and happily, the law disagrees.
Whatever the law, everyone has the right to full information about their choices, politely shared and clearly stated. Thereafter, their choices are up to them (within the law).