dybmh
ויהי מבדיל בין מים למים
There is a big difference between getting circumcised as an infant vs. an adult. In a religious family where the adult will likely want to be circumcised the parent is doing them a favor by getting it done as an infant.Willingly? A baby? Even a small child would not be able to give fully informed consent. Why would it matter if it was left up to the individual? If you're right they will still choose to "participate in a cultural and religious practice" no?
NIH.gov - A 'snip' in time: what is the best age to circumcise?