Corn is an excellent bait for the smaller carp, i use maize as it is a lot harder and is more resilient to to crayfish etc. Yes carp suck in the bait, a lot of fish without teeth do. Carp have teeth in the back of their throat where they can chew up very hard baits eg snails - nuts - crayfish shells etc so they tend to suck the bait deep into their mouths. By not putting bait on the hook, the "hooking" ability is not only magnified, but helps keep the hook to catch neatly in the bottom lip - Also if hard baits are used directly on the hook, they can prevent the hook from working properly and the likely outcome would be to pull the bait out of the fishes mouth or the fish would just spit the bait and hook back out without getting a hook hold.