The renunciation is rarely of sex alone. Monastic systems generally take three things together, property, sex and self-determination, and the third is often the hardest to sustain.
Christian religious life formalises this as poverty, chastity and obedience. Nothing is owned individually, and obedience places the monk under a superior in matters that would otherwise be his own, including where he lives and what work he does. Buddhist ordination differs in form and converges in effect: a monk owns robes, a bowl and a few permitted items, may not handle money on the strict interpretation, and lives under a code governing conduct in considerable detail.
The reasons given divide into three. The energetic argument holds that sexual energy is a resource that can be redirected, and it appears in Hindu and Buddhist yogic literature in frankly physical terms and in Christian ascetic writing in less physical ones. The availability argument, which Paul makes explicitly, is that a person without spouse or children can be sent anywhere and can lose everything, which is a practical claim about mission rather than a claim about purity. The eschatological argument holds that celibacy anticipates a coming state in which marriage does not apply and is a visible sign of it now.
There is also an institutional consequence that no tradition advertises. A celibate clergy cannot found dynasties and cannot leave church property to heirs. The enforcement of clerical celibacy in the Latin church from the eleventh century coincided precisely with a campaign to free church property and appointments from lay and family control, and historians generally treat the two as connected rather than simultaneous by accident.