I think that sounds backwards. People decide whether they want to have babies and seek out an employer whose environment works well with that life choice. So if you as an employer see parents as typically older (therefore more experienced) and more stable than non-parents, you would provide benefits that would be attractive to those people. I am not saying this is necessarily the case for parents vs non-parents, just that some employers might see things this way and act accordingly.

On another note, I don't think it's a good idea to pretend like this is simply another in an endless variety of choices people make about their lives that can be incented one way or the other. When people have kids it tends to alter the way they see the purpose of their whole life. It's not "oh sweet, I can get a tax credit if I buy a Prius".