There seems to be a trend developing among cable systems, and now perhaps satellite services, to move non-commercial channels (meaning low profit channels) to higher priced tiers. This has been happening a lot with Turner Classic Movies especially on Comcast systems.
The speculation is that while the systems usually get time in commercial shows to run their own local spots they don't with TCM because it's commercial free. By moving it to a costlier package the cable companies figure they can at least get some of TCM's loyal viewers to upgrade when they would otherwise not do so. This may very well be the case with DirecTV and PBS Sprout.