also for racers who suck it's used for detuning the tip and tail edges slightly so slide turns easier, it's for people who can't handle a course being on edge the whole time and who bank on washing out tips and tails
i usually do my edges and then run a gummy stone in the reverse direction from my filing to pull off shavings and burrs
nothing detunes a edge like savagely beating it on concrete, but seriously if all you want to use the skis for is rails take them to a shop and ask a tech to run then over the brown belt at a 45deg angle, after that you wont catch on pretty much anything
If a ski is properly filed / gummy stoned before you start hitting rails, the edges are less likely to crack, will last longer, and are easier to tune once they've been significantly worn down.
i was just gonna say the exact same thing. dont bitch about edges pulling out if you dont detune them and deburr um every once in a while. it helps a ton. files work, but i really like using coarse belt sander belts (without the sander if you dont want your edges overheating hardcore)