So I'm just gonna guess that you don't have the space, to get ducks. Ducks are very good at eating snails, just give them a bowl of water to wash it down, and the damage snails do to your crops will immediately be cut down. It's also a thing about money too, I guess. Not like Ducks don't need any extra food.
I would love to have ducks; they are awesome (and they and their eggs are tasty). However, I live in an apartment (with a dog), and the only reasons I can get away with a real garden is because I’m on the first floor… and the leasing office doesn’t care what I do as long as I obey certain community rules. I’m sort of at the back end of the property, and my apartment faces a courtyard of sorts; no one driving by or even through the parking lot can see my garden.
A neighbor even farther back actually has a rooster, but I’m not sure that was actually approved. It’s a lovely young rooster with copper-red feathers with black tips. I call it Copper, though I don’t know what the owners call it. I tried feeding it snails one day, but it was too scared of me to do more than peck at one or two while keeping an eye squarely on me. Probably because I had recently been chasing it LOL. I’d be very happy if it hung around my garden, but I rarely see it, mostly just hear it cock-a-doodle-dooing some mornings. Besides, my dog would also keep it away with barking, etc.
There is also a pet limit, so even if I could swing having ducks, it would have to be like one duck….