Not a cultural (or religious) norm; father and other males are uncircumcised
Unnecessary (benefits are inconsequential): Most of the world is uncircumcised and, with proper hygiene, there is a low problem and disease rate
Complication rate is too high, including a poor cosmetic result
Painful procedure (analgesia is often inadequate)
Hygiene is teachable and attainable
Circumcision rarely becomes medically necessary later in life: old data (1968) suggests a 1.7% necessary rate. Today, there exist newer non-circumcising techniques to address potential problems pf phimosis, paraphimosis, adhesions, etc.
There may be unknown or unstudied problems like psychological trauma, less sexual pleasure
It is unethical to perform an unconsented (by the child) "genital mutilation"