Why so? Because it takes a long time to move minerals/ships/colonists back to Sol?
Mostly this. You are of course right that there are uses for it, but most of that can be accomplished in other, easier ways. If I want a research planet, it is easier and faster to colonize Mercury - perhaps slower to terraform, but that will be outweighed by the much, much shorter route of the colony ships, and I have plenty of infrastructure. Or just move it to Callisto, which is already being terraformed and has an MK anomaly and a handful of research facilities.
If I want to utilize the minerals anyway, I believe (but might take another look) that there are sufficient amounts in the nearby systems, and at this point, it makes little difference if I have access to 4 million or 24 million duranium. I can't mine either amount fast enough for it to matter for my current production levels.
I will probably want to colonize it eventually for the minerals once production levels increase, but if it had had more jump points, it would have been an invaluable investment as a staging point for further exploration with own shipyards, maintenance facilities and ground unit construction. But mostly I was just dissapointed that I couldn't do that, more than disparaging the usefulness of it entirely
My last great game in VB6 died while I was preparing for such a satellite colony with the intention of giving it indepence when it was sufficiently developed and start a civil war. Looks like that'll happen in another system