It's good PR because it's the right thing to do. I certainly hope it's a trend. It's fairly well-established that humans make babies and need time off work to properly care for them.
Basic Humanity. Belief that existing laws in the US are pathetic and don't go nearly far enough.
Or staff retention, if you insist on degrading human relationships to purely economic terms.
As you put it, it's a "Belief". I'd rather call it a point of view or even a political opinion.