As noted here before, there seems to be a pattern regarding episode broadcasts in that it seems like PBS spends anywhere between six and eight weeks playing more current/recent episodes, then maybe a week's worth of older episodes (two if we're lucky); or, instead, will have one week where newer and older episodes switch every other day. On a similar token, another forum member (I forget whom) mentioned that they of these said earlier episodes, Season One gets the jilted the most.

Any way, I've done some thinking, perhaps too much thinking, and I believe I may have come up with a list of theories as to why older episodes are rarely shown any more; see if you agree with any of them.

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1. They're too "dated". I think Season One would be the biggest offender of this, there are hardly any computers, hardly any cell phones (though in "Arthur, World's Greatest Gleeper", Muffy accuses Arthur of gleeping her "cellULAR phone", which is pretty bulky), TVs are still relatively small and boxy, among other things. Pop-culture references would be outdated too, therefore, little kids probably wouldn't understand them.
2. Voice inconsistencies. Since like 2005 or so, the kids have had almost steady and consist-sounding voice changes (despite both Arthur and D.W. being too high for their characters), they probably think little kids are going to be confused as to why Arthur and D.W., and certain other characters sound one way one day, and another way the next. Binky, especially, had a much deeper and kind of deadpan-sounding voice in Season One.
3. Character continunity. Again, I think Binky is the biggest example of this one - throughout the entire first season, and occasionally up until "Arthur's Big Hit", he was THE school bully, all the kids avoided him and ran away from him, he came across as mean and pushy... it would probably be odd for kids to see him as a bully that every one runs away from in one episode, then see him as nice and one of the gang in another. Brain, too, is more nerdy (big comic book collector), and much more sloppy and unorganized (hates cleaning his room), which seems odd for his character today. Both Fern and George are background characters who rarely ever spoke (Fern moreso since she's far more outgoing than she used to be, while George is still shy and withdrawn), among others.
4. It may even be a case like with the Old School DVD volumes of Sesame Street, where they probably feel the older episodes are "for nostalgia", and "may not meet the educational needs of today's preschool children". Just a thought.

Those are some of my theories, what do you guys think?

DVD releases have been weird.

I think Season 10 is the only full season that had a DVD release, and I think here recently, there was a compilation set that had mostly older episodes... I forget what the theme was, but I think it had some thing to do with the outdoors or some thing, because I think episodes included were "Arthur Goes to Camp" and "D.W.'s Deer Friend".

They've aired old episodes before. Matter of fact I remembered seeing Arthur's Eyes and Arthur Goes to Camp in 2012.

I've just thought of something! I rarely see older TV shows on any channel. In 2006, I rarely saw shows from earlier than 2002. Now I rarely see them from earlier than 2006. Is it because older shows are more expensive? Is it the same with older episodes in a series?

You know, at this point in time, I may be "being difficult", but I'm just going to consider the show as being "off the air"... they rarely show the good older episodes anymore, I dislike much of the newer episodes (I'm still giving Season 16 a fair chance), and I feel like I haven't seen the show in years anymore, so, as far as I'm concerned, Arthur on PBS is now dead to me.

You could always see older episodes on Youtube and PBS' own site. Just a thought.

True, and I have a number of my favorite episodes on tape... still, it doesn't quite feel the same, but oh well.

Can't ask for everything. Sometimes it's always best to accept things that you have now. That's all I can say for this.

I asked a friend at PBS about this theory that the first  season shows don't air as often as later seasons and it doesn't seem to be true. The latest season released gets extra airtime and then once a newer season comes out that previous season gets put into the same rotation as the other shows.
So season one shows will be aired as many times as season 15 on average. On average just becuase of where they are in the rotation at the end of the year that you are used for counting.
So the kind of numbers she gave me from looking at the broadcast shedule from Mid Sept 2012 to Mid May 2013 are shows from season 16 will be aired 68 times and shows from season 4 will be aired 20 times. But season one and season 4 airing numbers are the same.
There is some distortion due to the shows that are aired for special events such as the special airing of April 9th in the aftermath of the Conneticut massacre 2 month ago. Also some things like the elections or inauguration or olympics might have some special shows brought into the line up for those weeks.

So  it's just a matter of patience if you haven't seen season one for a long time.
Sometimes broadcasters publish their future broadcast dates well in advance if you look for it on the website. I remember seeing BBC one once and it listed the dates of upcoming Arthur shows well in advance.
I haven't checked for the PBS broadcast schedule.
On a side note the way the shows are paired does not change.

Thanks for shedding some light into this.

Yeah too bad though . It was a pretty carefully done high end episode with the McGrady stuff and all, even it it was too heavy on message and had a bad actor for a guest star, and the charicature was ugly.   Only a mature kid's show like Arthur could tackle a subject like cancer and dying and now Lance screwed it up.  Why did they ever do a show with that guy? Anyway this show could be "the lost episode". I'm not sure which emoticom face to use for this.

Probably this.