Because a hungry bird is a foraging bird. If the first thing they want each morning is food and there is very little or none in the feeder, they have to hunt for food to assuage that hunger. CX are even more hungry than the typical chicken, so that drive to find food is heightened considerably in this breed....they will walk every ounce of fat off just trying to find food. Give them a good place to forage and you will be amazed at how they out-forage any other breed of chicken, hands down!
Trust me, if you don't feed them until evening, there won't be a speck left for the mice if you only feed what they can eat in those evening hours. Any scraps left over until morning they will finish off before they leave the coop.
Try trough style feeders in which you can gauge how much your birds will consume in one sitting then just make adjustments as their feed needs fluctuate according to their growth, needs and the available forage.
As with any developing animal or human, exercise is important for proper bone and muscle development, as is the uptake of calcium from the blood stream to the bone matrix that happens when weight bearing exercise is performed. If you feed calcium to birds that never move, that calcium in their blood stream can inhibit renal function...give the same birds feed with calcium and then make them exercise and that calcium gets turned into strong bones instead of kidney problems. Strong bones means good mobility, no leg problems.
The heart is a muscle. Muscles need to exercise to perform properly...if your birds never move except to the feeder and waterer, then when they have to bear more and more weight and exert more effort on their cardiovascular system just to walk or to withstand rising temps and humidity, it results in "flip" and ascites as they go into heart failure.
I've read so many posts on this forum and others about people who put their CX out on pasture and all the while also provide continuous feed...and then complain they are too lazy to forage. Got to be smarter than the average CX...take away the food and watch them scoot boot all over that pasture!!! All chickens are opportunistic feeders and CX are like a typical chicken on overdrive..they eat what they have in front of them as long as it is in front of them and need never step foot any further if the food is there when they walk past it.
Start them young on free range, feed them light, confine them and feed them a little heavier(more protein) at the end to lay on some fat under their skin and soften those free range muscles and you will have a fine, healthy and cheaply raised bird in the end.