Circumcision is a choice for adults suffering phimosis or other issues. Alternatives do exist.
In some cultures, at some point, it may have become a ritual for adulthood or symbolism, it was never practiced on babies.
In Egypt, practicing this on the very young occurred with all the mixing, the confusion, the papyri to 'Archangel Michael' and the rest of the crap as the population devolved massively. Unfortunately this (updated with the most severe practice on Earth of cutting up to the skin mid-shaft, mandated by jews in the Middle Ages) reappeared in England and America in the late 19th century, becoming a global standard for how it is done now.