Its like going to a nice restaurant with your spouse for your anniversary. You wouldn't go if they didn't actually give you the food to eat.

Is it clear now? Catching fish is the reason to go fishing.

And using bait? The second most important thing about fishing is all that stuff you learn, buy and do so you can catch fish, or more of them. And at least for trout, bait is inferior to SOME fly patterns and techniques.