Because it is my NATURAL state of being! It is how a male is supposed to be on earth. The only purpose of semen is in reproduction, to continue the human race or your lineage. If you're not doing that, what is the point of releasing semen?
Those who have not transmuted or sublimated their sexual energies will always seek pleasures of flesh, because that's the only pleasure they are habitual to seek. When you use this energy wisely, it will not feel like a burden. Do you feel compelled to pour out blood from the body daily? No because there is no pleasure involved there.
Likewise when you find other pleasures from utilising this energy, you will realise the potential of it and the folly of releasing it for momentary pleasures, which always follows with weakness of body and mind. Be it material growth or spiritual growth, conservation of this vital fluid is important.