The population of the world is (according to the US Census Bureau) 6,709,531,432. Of these, an estimated 143 million are orphans. There are plenty of kids in the world.
Children are a financial drain. While the joy of parenting far outweighs the costs, the costs are estimated to be about a quarter of a million dollars to raise a child to 18 years of age. The time investment of raising a child is immense. The responsibility is epic. The impact on future projects would be drastic.
Mike Merrill is great with kids, but he has experienced no desire in his 31 years to have his own and claims, "While I look forward to hanging out with my friend's kids, I don't wish to have children of my own."
In light of these factors, it makes sense to reduce the chances to nearly zero and have a vasectomy performed.