I’m uncircumcised and am glad my parents left it alone.
I had always assumed it had to decrease sensitivity (wasn’t even aware of the rest discussed in this thread) by the simple fact that mine gets irritated if the skin is pushed back while I’m wearing underwear.
I know two guys, my brother and a friend, who both had it done later in life. Both agree that it cuts down on the sensation, and the friend even had trouble maintaining erections for a while because of the contrast.
I only ever had one gf mention it, but there are a lot of things in the media (like an episode of Sex in the City) which make it appear we should feel inadequate for not being cut. To hell with that.