Just judging by the other articles featured on the same page, I'd say this website is a shill, not for moms and dads, but for the liberal agenda. Just at a glance you can see an anti-hunting article, the godless Brangelina family at home "praying" (to whom?), and this pap. Contrary to the nonsense in the article, I can't think of a single major company that doesns't have maternity and paternity leave, and a lot of small companies here in Kansas City offer them, too, including for adoptions. They don't need their respective states telling them they have to offer M&P Leave, they already provide it. California and New Jersey are liberal bastions where life is legislated, not lived.
As to the question, the issue of fairness has nothing to do with it. Singles normally don't have kids, and the companies I know that have M&P Leave give it to singles when the do have kids. Why should singles get something like M&P Leave when they don't need it for it's stated purpose?