Going off the runway due poor braking action is also bad for your turbine blades (among other things). That aside; if they put on so much sand that it gets sucked into the engines, it's too much. The idea is to spread a thin layer, diluted with hot water, to make the sand grains freeze onto the surface of rime or ice. So you are taking off from a sandpaper, rather than a sandbox.
I suppose the blade erosion on reversing propellers may be more of a factor, really.