You need to bear in mind that cold water is denser than warmer water so the coldest water is on the deck. Therefore carp, being cold blooded, will only drop to the deck for one reason at this time of year and that is to feed. However, since we're approaching the end of winter, their metabolism is as slow as it gets, and they need less food, hence bite times on the deck can be very, very short (less than an hour a day). For the remaining 23 hours, zigs give you a genuine chance of a bite. It's the main reason most angers blank all winter - their hookbaits, being on the deck, are nowhere near the carp. Zigs should not be ignored, particularly in winter.
Of course the info above is a generalisation. This winter has been the warmest in years and some waters are kicking off, even over bait.