In my early years a s a Scoutmaster I was upset when my Scouts chose to miss a meeting or outing in favor of another activity. It would not be too much to say that I took it personally (at that point I was doing most of the planning and leading anyway!).
My initial response was to adopt a policy similar to one I have read many, many times in Troop-specific policy manuals; a set percentage of outings and meetings Scouts must attend to be considered active and a ‘leave of absence’ policy that outlined how to suspend a Scout’s active membership while they pursued another activity.
That many Troops have similar policies reinforces the idea that this seems to be a reasonable way to handle the issue. What I came to find, however, was that this approach really cut across the grain. Like the old preacher said it was ‘like washing your feet with your socks on’, it just didn’t feel right.
Several years after abandoning my carefully written policies I have found that Scouts are no less active and more likely to follow up on their leadership commitments when I simply trust them to do so. I encourage you to take a good look at how you handle the issue in your Troop.