I never been in a duckie but fro m my very limited perspective they do is allow someone with limited skills to get on the water
We ran a canyon with a couple of 3+/4 sections last sunday ,2 hard boaters (one being myself ), 3 rafts and 3 duckies
2 of the brand new duckie riders got in the raft for the knarly bits but the duckie did allow the one guy who had a couple of river runs under his belt to get on the water ,sure he flipped but he just got back on
no way it would have ever been possible in a hard boat ...just too much to learn
we had 2 commercial guides and the owner of a swift water rescue company so it was all reasonably safe
edit :Will i try one ?probably not