After seeing a post on a Facebook group pretty recently reminding of the looming final season of "Arthur", I decided to view select older episodes, plus select episodes from beyond Season 11 that I never got to see due to my loss of interest in the show in July 2007. My loss of interest was due to excessive reruns, as well as the newer content being dull. I have to say, after realizing that the end is looming, i felt that this is a good opportunity for me to view episodes I missed out on. it would be a case of not appreciating something more until it's gone. More like "almost gone".
There have been plenty of rehashing of plots in the later seasons. For exampke, "MacFrensky" is basically a rehash of "Nerves of Steal", only without the shoplifting. "The Butler did What?" seems to be a rehash of a season 11 episode where D.W.'s imaginary friend, Nadine, went missing (she was on vacation, just like Bailey did).
With the plethora of plot rehashing since around Season 13, could that explain why most of the older episodes are hardly shown on PBS nowadays?