Birth rates are falling all over the world. People aren't childless despite trying. They're just not trying, for the most part.
That's simply not true. Worldwide, sperm counts have dropped by 50-60% over the last 50 years (and the decline is accelerating). Sperm motility has been declining as well. These factors have a direct impact on fertility despite trying
Still more than enough to get a kid unless you have other issues, biology might play a role but it isn't the main factor here. Plenty of country with massive baby booms right now