I think your generalizing a bit there David as a boilie can be many things with the only similarity between them all being the cooking process.
Most are over flavored hard inert balls sold in a fancy tub, no dispute there.
However Some of the very best ones made by proper bait companies offer a nutritional diet that cannot be found in other baits especially halibut pellets and spam.
Proper food recipes put together with good ingredients like natural seeds, milk proteins, fresh eggs, spices, meat proteins, natural sweeteners etc etc and these types of baits offer a hell of a lot to both the fish and the angler.
Unlike a lot of boilies you can buy, mine go mouldy if left in the fridge longer than a week.