Your friends don't know much about fishing. Bobbers are extremely useful tools. That is why they are made in seemingly limitless styles and sizes. The greatest advantage afforded by the bobber is it allows you to cast into areas your boat won't go and suspend the bait at the proper level to catch the fish at their current depth. Schooling fish will suspend themselves at certain levels depending on food supply, water temperature and structure. The bobber allows you to hit these depths perfectly. Since some fish are very sensitive to resistance, the size and shape of the bobber will allow you to catch them unaware.
Tell your friends this: More record fish have been caught employing a bobber and live bait than any other rig.
There are lots of other ways to fish and you should try them all. They are fun and extremely effective for certain species. But if you stop using a bobber because your simpleton peers are too stupid to do the research, you are going to have some very bad days fishing.