The flap of the penis, if not removed, will retain urinary secrements and with that microbial, bacterial pathogens. Wherever one sleeps, sits, has sex with, potentially can carry such bacterial pathogens. Additionally, if not removed, the flap of skin will cover the penile head, thus causing a lack of aeration, thus odor manifests greatly. Odor, is a sign of pathogen, bacteria, as it is produced by bacterial cells during lysis.
As for increased pleasure, I am aloof in that.
Removal of the skin flap does make sense, proliferatively speaking.
As its removal would allow the release of sperm without epidermal hindrance; thus can fertilize the female's eggs en mass. If one isn't circumcised, then the skin flap would get in the way during sexual intercourse, spermicide would result as half or more of the sperm count would be trapped in the linings of the skin, instead of making its journey to the uterus.
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