I have given a reason why incarcerating adults who have not committed a crime against their will is obviously immoral, namely because freedom is one of the most fundamental human rights. Of course, there can be reasons that might outweigh this right, for example when someone has committed a serious crime and there was a fair trial. Another reason would be the medical assessment that the person would likely severely harm himself or others. For the latter, the hurdles are extremely high. You can ask your lawmakers why they think they should be high. They will probably tell you that's because freedom is one of the most fundamental human rights.
"Caring" for someone is traditionally not considered a sufficient reason. And that includes parents, who are definitely not allowed to lock away their children indefinitely (as a reply to the other poster, who seems to be even more confused than you).
> you're arguing they shouldn't be held to the same responsibilities as other citizens because they can't help their situation.
I have never argued for such an absurd claim at all, in any form whatsoever.