Because yahweh likes the smell of rotting foreskins, per his own words.

This means that Abraham made a tall pile in his house of the foreskins from the many people that he had circumcised. He piled them, one on top of the other, in his house and a stream of blood flowed from these foreskins. The Holy One said to the angels: let us go to Abraham’s house to visit the sick. The angels said: Lord of the Universe, it stinks and it is quite repulsive in Abraham’s house, because of the foreskins. God said: in my eyes the smell of the foreskins is much better than the pleasant odors of all the incense, as the verse says, “I will betake me to the mount of myrrh”