There is already a thread with the question why sidecars weren't run on Sunday. Answer was they had not qualified yet. But I agree with you they should at least have run something on sunday before the Superbike Race.
Other question was why not Superstock on Monday. Answer was to much laps for the riders. Would have been round about 10 Laps. SP(4)+SS(4)+Q(2). Are 10 Laps to much? I remenber in the Past SP1 and SS were always on Monday on the same day plus qualifying. Friday in the past was Senior(6)+Lightweigth(3)=9 Laps.
In Motorsport (not only TT) I have often the feeling that organisers waste time. That is so often the case that I don't believe there are suitable reasons for it. But if there are reasons they should communicate it better. Otherwise it remains the impression they waste time for purpose.