Men without foreskin experience less pleasure from sex, simply because the foreskin protects the head of the penis so that is doesn't get exposed to fabric, elements, whatever else.
The reason the head of your penis is sensitive is that it hasn't been over-sensitized. The foreskin keeps that from happening. Once the head of your penis is used to feeling the material or whatever all day everyday, it simply ignores the feeling. Much like the skin on the rest of your body ignores the feeling of clothes; you don't ever think about them because you're used to wearing them.
Men who have that foreskin aren't used to the constant touch of cloth, so the head of the penis is not used to a touch of anything save for that foreskin, which is why most men who are uncircumsized seem to enjoy the sensation of touch much more than men who are circumsized.
