I think you just made my point. Thanks.
Prevention of colic: daily free movement.
The main causes are
Sudden changes in diet that cause stomach and digestive upsets
Insufficient drinking water
Horses that bolt their food or for some other reason don't chew it properly
Sand or dirt in the intestines
Although having access to a grazing situation does make it easier to allow a horse to be constantly browsing this can be replicated by the use of slow feeders and where you have horses with metabolic issues that becomes a necessity where grazing has to be restricted
Exercise can and is provided by the use of horse walkers, riding and lunging
No one here is advocating having a horse shut in a stable 24/7
Horses can be neglected in any situation - including when kept out at pasture 24/7 - which is how most cases of laminitis occur