Partial truths

Some primary songs really bug me. Take, for example, the song “The Family Is of God”, which includes the lines

A mother’s purpose is to care, prepare,
To nurture and to strengthen all her children.

Are you kidding me? How about telling the truth: The purpose of human beings is to care, prepare, nurture, and strengthen children. (And not even just their own children, at that.)

So why the need to present this partial truth as a contrast to a previous verse describing a “father’s place” (which also only gives a partial picture)? This whole cultural need within present-day Mormonism to try to place mothers and fathers (well, maybe actually women and men) into neatly separated boxes strikes me as weirdly wrongheaded, and possibly even dangerous. So how did we get into it?