I empathize with parents, but please don't make it sound like it's a selfless act they are doing for the good of society.
Also, childless couples/singles get taxed at quite a high rate (after any returns) vs parents. You compound that over 21 or whatever years it takes for kids to become "productive". Furthermore, people who choose to stay childless still have to work and pay higher taxes till the age of at least 66 in US. Life expectancy for males is 78, so that gives you 12 years. Social security is in no way enough, and you must survive on pension that you paid into for your retirement. So the child that I helped raised with my extra taxes and without any preferential treatment at work will never even come close to paying me back.