Why no season 6?

I agree.

According to my mother, who was a teen at the time this show aired, she said that the marriage of Jeannie and Major Nelson killed the show because there was no more sexual tension between the two characters. So ratings plummeted, and the series was canceled.

I think it would have been nice to see them have a kid, whether boy or girl, or even twins. Even better if they could have magical powers like mom ;). Plus, it would have made great drama to see the evil sister try and get Jeannie and Tony divorced and failing miserably, hehe.

Even better, it would have been nice to see a proper series finale with the show, something to give them a proper send-off.