The show was shot entirely on standard definition videotape. There would be no point or benefit in putting it on Blu-ray other than to save a bit of disc space. You would get no improvement in picture quality, this is as good as it can look.
Not entirely true. It can be upscaled to 1080p, but the quality will only be slightly improved. Like for example: slightly more details, stronger colours, better compression, less compression artifacts and lossless audio.
If it was released upscaled on Blu-ray, i don't think it will sell so good. Many would complain about the poor picture quality and more and more people will hear about and people will stop to purchase it. But, for some big fans of the show, it will be worth it to buy it even if it's just upscaled. For me, i personally don't buy upscaled BDs. I don't think it's worth it.