Outside of injecting ones higher power into it, evolution has no purpose, it is just something that happens. Humans evolved to love sex (which a lot of times leads to babies), and to love babies and children (which keeps babies and children alive). Not everyone loves sex and babies, but research shows that they are the two strongest things used in marketing, puppies are the third thing, which also hits on the baby instincts. Like electric lights for moths who evolved to use the light of the moon, birth control is a new thing that complicates how we evolved, but that is just for the people who can access, afford, and use them correctly. Abortion too, as most people these days are not cool with infanticide or leaving living healthy newborn babies on the rubbish pile.