I hear you, but the problem is that the alternative is much worse. These indefinite detentions lend themselves to all manner of corruption. Maybe a prison guard doesn't like you and falsely claims you committed a violent offense, just to keep you inside. Maybe a fellow inmate attacks you, and when you defend yourself, it gets registered as a violent offense.
The first element of due process is that a citizen be notified that the State is mobilizing its resources with the intention of depriving them of their life, liberty, and/or property.
Another core tenet of due process is that, once notified, you get a chance to submit evidence in your favor before an impartial adjudicator, precisely to avoid the issues in my first paragraph.