Why do you want commitment? Because not only do you want to have sex, you want an uninterrupted and guaranteed supply of sex; that is what you call as commitment.
“Not only should you be with me for one night; assure me that I will find you on the bed every night.” That’s commitment. You will not say that because it is so disgusting to hear, but that’s the intention. That’s what you call as loyalty, commitment, or whatnot.
Prakriti (physical nature) wants you to have it three times a day, and if you must have it three times a day, then the supply must be assured. And how to assure the supply? Through commitment and loyalty. If there is no commitment, then he may run away or she may run away.