People join the military for lots of reasons (patriotism, free college, bad family situation, and more) but we all recognize that funding the military and making life tolerable for service members is necessary for our society to keep working.

Similarly, people choose to have kids for lots of reasons (family pressure, want to pass on genes, etc.) but society's continued existence depends on people having kids, so it's on all of us to support the people who do have kids whether or not any given individual's motivation is noble.