When you put feed out in feeders it prevents less mess, and pests are not attracted to the source versus feed which in on the ground.
Feed that is at ground level is prone to ants being attracted, and not all the feed being eaten. I perfer feeders to ground feed, but then again it's your own choice.
Well, we have ants, a lot of ants, close enough to the chicken's run/coop that putting their feed on the ground isn't an option. Immediately when the pullets get here, their run will be ground and weeds with their feeder up on a cinder block, when they finish the weeds, we're going to put down a few inches of sand, and then put their feeder back up on the block, on the sand.
It will be a determined ant to get though all of that!
We also have opportunistic mice in the garage who, last summer, broke into our grass seed (silly us, we just left it in its plastic bag) and ate it ALL over that fall/winter, so we want to try to keep them from noticing the chicken's feed, again, feed in a feeder up on a block. Unused feed will reside in in its bag, in a sturdy aluminum trash can with a lid, in the garage. Worked well for the horses when I was a kid, I see no reason why it wouldn't work for chicken feed now.
Anti-vermin precautions are a big thing with the Animal Control officers who come to inspect my city's urban chicken set-ups, both initially and then once a year to renew the permit we all have to have.
Because anti-vermin is such a big huge hairy deal, we won't be sprinkling anything that's attractive to mice, ants, rabbits, wasps, squirrels, etc on the ground anywhere near the chickens unless we can be assured that the chickens will eat it or otherwise get rid of it before anything else notices!
Other situations are different, of course, but that's where we're at and what we have to do. So that's our reason for not just sprinkling stuff on the ground.