All the time. One of my rules that I will talk about tomorrow is "To catch more carp, cast at less." It might not apply with bait as much, but on a fly you need to find one fish that is eating or might eat, stalk that fish, and present the fly into that fish'a feeding area (usually a few inches). Without scent or bait, you have to trigger a visual response on a fish that mainly uses scent...that is the tough part. Even if I see 50 carp, all tailing and feeding like crazy, I have to cast at ONE fish in order to have success. When I see 100 non feeding carp...my odds go way down.
Sunning carp simlply are not feeding. You can occasionally talk one into eating, but it is tough, and usually the attempts result in spooking one which blows them all. In general...I keep walking and look for better targets. If I have no other fish around I will try to talk a summer into eating, but mostly I move on.
Sunning carp suck!