First, he's probably Jewish or Islamic. Both religions have their traditions. In Europe, sure, it's rare outside Jewish communities. In the US however, it's very common even among non-Jews. That is because there is medical evidence that suggests it's more hygienic. In fact, MOST men in the USA are circumcised. Like 80-90% of the male population in the country are. Statistically, half of all non-circumcised men will contract a medical condition related to their foreskin. It should be considered equivalent to a vaccination - sure it's optional, but it's not smart to not get a circumcision if the opportunity is present.