Why? This is so because food indeed is lord of creation.
Annam Vai Prajapati Stato Ha Vai Tad Retas Tasmad Imaah Prajaah Prajaayant Iti.
Food indeed is the lord of creation for from this verily is semen created. From this semen, all creatures are born. Therefore, respect your food. Annam Brahma–Food is a manifestation of the Brahman, a truth reflected also in other Upanishads.
Tadye Ha Vai Tat Prajaapati Vratam Charanti Te Mithunam Utpaadayante. Tesham Eva Isa Brahmaloko Yesham Tapo Brahmacaryam Yesu Satyam Pratisthtitam
It then says, those who practice this rule of the lord of creation, those who understand the value of celibacy, as well as the value of creation, those who practice the rules by which they know how to control and use their energies at the proper time in the proper direction, they produce couples. This Brahmaloka, Brahma’s world of creation, in which austerity, chastity and truth are established, are for them alone.
So, the seers of the Upanishads see the great beauty and natural innocence in the sexual life and parental love, linking it to the deeper and higher energies of the cosmos.