As a general rule of thumb, rules are usually set in response to an action that is deemed undesirable. Without being there everyday, I have no real way of telling, but I would hazard that apparently the coach feels there is a need to implement a new policy in order to cut down on what he now feels have been excessive absences without perhaps valid excuses. He may be feeling taken advantage of because of a more lenient/more adult/personal responsibility policy in the past that has been exploited.
Personally, I know how this can feel. Several years ago I was coaching a couple of runners who came to me and told me that they had to miss Tuesday practices because that was the only day they could get math tutoring. At the time, we had to use a local HS track, and Tuesday was the only day we could get access to it, so we typically scheduled our track sessions for that day. I agreed that the tutoring was more important, and we agreed that I would just give them the workout to do on their own.
Until the Tuesday I was driving to practice, and came across the "Tutorees" riding mountain bikes down the road. Seems the Tuesday tutoring sessions were just an excuse to not come to practice and do whatever they felt like. More investigation revealed that these two "5K" runners were actually among other things, doing 26 mile long runs to prep for a marathon, without ever mentioning it to me...so I was always scratching my head wondering why they seemed so fatigued all the time on Mondays, etc., why all the 5K and under race times were way off, so forth.
My point is this - not pointing a finger at you, but look around you, and maybe you will see why the coach has changed his policy.