Should a soldier's pay be reduced for the allotted time missed (e.g. missed appointment time, excessive sick call, etc.)?

Sure-- when they start paying overtime to soldiers for all the extra hours they're at work doing nothing waiting for the leaders to get their shit together.

My issue is that we spend so much time harping on soldiers for missing appointments, or not cancelling at least 24 hours out, but nothing happens on the opposite end. Several times I've had appointments cancelled on me the day of with no notification. I've also had them send emails cancelling the day of to my work email. Unfortunately I work nights. If we are going to dock soldiers pay, do we also get to dock the people conducting the appointments?
As far as excessive sick call, are the individuals faking illness? Are the medics/docs being overly gracious? Or are there also instances where the actual issue isn't being resolved. We all know someone who was told they had little or nothing wrong with them only for it to be a major issue.
I think it's important to look at this from all angles. There are people with whom your question applies, and there are those that have been faulted as well.

Well we know that there are federal code statutes which make it so that we cannot take a soldiers pay for such things. Having said that, the luxury of salary is that we can take their time. I have had the opportunity to serve as a platoon sergeant in a headquarters platoon. I encountered many soldiers with all manner of appointments. I never denied them an appointment, however, I did require appointment slips from all of them and held them to time standards. Additionally I gave them tasks, conditions and standards. I explained to all of them that their personal appointments would not affect my deadlines. If something was due to me on COB on Friday then COB Friday would not come until that task was complete. I was also more than willing to counsel a soldier on failing to complete a mission, with the corrective action being work on days off or into the evening. Understand that this also meant that I would have to be there. That's just part of leading from the front. But it wouldn't take long before sacrificing time to accomplish the mission encouraged soldiers to be more efficient. Yep malingering and appointment dwellers are a problem, but I never met a soldier who would rather duck out of work on Monday if they had to give up their Friday night or Saturday to make it up.