Simple answer. Revenue stream. I get the sense that Disney is preparing the network for sale by putting it in the best financial position first. Yes, WLS could show evening movie classics, or they could show paid advertisements and bring in some more revenue. You must ask yourself this question: Which brings in more revenue in the wee hours of a weekday? A 30 minute advertisement (contiguous cash influx) or a classic movie which requires financing, albeit low, and a few advertisements (noncontinuous cash influx) during the movie breaks?
I realize that WLS has personally attacked your viewing habits, and a tradition has disappeared, but realize that you are night owl and that the majority of Market 3 is not awake with you, but when people are, WLS would prefer to make a bit of easy money (automated) then spend it.
Personally, this is a smart move.