Nothing is more heart breaking to me than to have a girl with a nice set of breast with nice responsive nipples only to find out that their nipples have no sensitivity and that they can't feel anything.
This situation has come up a couple of times were I start playing with the girls nipples, licking and sucking on them ever so gently thinking that this would be good foreplay before the action gets going. The girl sees me putting in the effort to please her but finally tells me not to waste my time as she cannot feel the stimulation on her nipples unless I really pinch them really hard. What a shame as I take good pride when I could get a girl all hot and bothered.
I've heard that alot of girls with implants lose sensitivity in their nipples. But I was unaware that girls with natural breast and responsive nipples could have little sensitivity also. It's just a major let down when that happens.