Compost is easy-- unless you live in the Atacama desert, if you dump it, it will rot. A bin would make the combination of food scraps and other compostable waste and manure easy to combine, and keep the food from the rodents and other critters. We have worm bins specifically for the food waste that doesn't get thrown straight in the coop and compostables (q-tips, dryer lint, etc), and we add coop bedding straight to that for worm bedding. Works nicely--worms like the manure!
Worm bins are "cool decomposition", manure piles without loads of bedding are usually "hot piles" and will get too hot to support worm populations. I don't mention that to get you confused, and one is not necessarily better than the other--just so you know!
