I'm curious why not?
...Hitting 40 and no desire?
Pretty much. I just have no desire to. I love being able to vacation 2-3 times a year without worrying about baby sitters, or wondering what my teenager is doing when I'm gone. I love being able to wake up and I'm responsible for myself and myself only.
Besides, I have 14 nieces and nephews. And I have sort of been daddy 'lite' anyway. I'm the only "successful" one in the family so the older ones are always coming to me for education and career advice.
Also, there is no guarantee that your kids will turn out the way you want them to be. Your son could grow up to be some c00n ass nikka diluting your genes. Or your kids could have some physical or mental handicap issues. That stuff takes money if you want the best care.
The world is over-populated anyhow.