It’s not just about the crop, these over wintering carrots were harvested in late winter, all around the carrots are weeds which happily grow together in the winter, the one in flower is red dead nettle which will be visited by early emerging pollinators like bumble bees on warm late winter sunny days when they are active. Any weeds covering the soil in the winter are moping up surplus nutrients and protecting the soil from weather elements and feeding soil life energy from the sunshine increasing soil carbon.