Dirt and other sediment will settle in and fill the spaces between the ballast stones, locking them up and causing the roadbed to be non resilient, cleaning this debris out restores the resiliency and makes the ride smoother. which among other things extends plant life.
Grinding removes tiny hairline stress cracks that start in the rail through normal use, before they become much bigger and threaten the rail with failure… Plus, the proper “ride” profile is restored to the rail head, for a truer ride along the rails
Yea I saw the Loram ballast cleaning equipment while I was ridding down the road, so I turned around and went back. It’s amazing to watch that equipment at work.