They show the same ones over and over again. They've shown some season 1 episodes only once and when Jo came on the show, that whole season, twice, I think. I mean cant they change it up a bit??

i noticed that too - they seem to just keep repeating the same 20 or so episodes over and over again

It ticks me off when networks do this. TV Land used to be famous for airing the same episodes of "The Golden Girls" and "The Nanny" all the time. Now I don't even bother with TV Land. Thankfully I'm blessed to own these series on DVD. Logo also does this with "Roseanne". They air the same episodes over and over.

I know what you mean. I've been kinda doing my own little research and been keeping a sort of mental log of what they air and this is what I've observed. They tend to air about six episodes from each season before moving onto the next season and they seem to all be the same 6 episodes.
I don't think they are commissioned to air every season and every episode in its entirety. They probably only have the rights to air certain episodes or maybe that's all they could afford to air. I'm not too sure how all the logistics work when it comes paying the licenses.
It's different for shows say like for example The King Of Queens which is more of a current show and still currently plays 24/7 in reruns on multiple channels. Shows like that will air pretty much air every episode still cuz it's still current.
I remember back in the day in the 80's and early 90's when The Facts of Life was still a recent/current thing they would air every single episode every day in reruns like they do today with current shows but I think when a show hits past a certain point in time and age they cut back on the number of syndicated episodes. They only buy the rights for a handful of episodes since it's already a very old show.
It also has a lot to do with current interest in popularity.
It does suck though. I wish they would switch it up a bit but that's why I'm so glad I finally got the boxset. I'm finally seeing episodes now that I forgot about but yet I remember so well. If you can fit it in your budget I would suggest getting the boxset.