Why exactly are custodial parents legally allowed to refuse to seek child support if the best interests of the CHILD should come first?

[C2H5OH]

Originally Posted by Xen Master

Well, one could argue that there should be a legal duty to seek child support and/or to voluntarily get a paternity test and pay child support if you suspect yourself to be a child's legal father.

Uhh, the two underlined, italicized things are mutually exclusive. You need to work on your 'basic logic' skills before you start straining your brain on complicated subjects like this.