Religions against ?

So many religions are against and I just don't get it. We are here to reproduce, to keep the human race alive not to just die. What is the deal with many religions requiring celibacy and abstinence or even removal of the testes or ovaries. To me it is more of a sin not to have . I'm not talking the vulgar ideals of ographic I'm talking the original act that is tainted by vulgarity.