Stephen S. answered 12/29/19
Reading and Writing Specialist: phonics, ESL, essays, and SATs
The best way to answer this is to imagine what government would be like without the Sixth Amendment. This one directly responded to the colonists' complaints about indefinite, arbitrary detention and secret trials, the kind of legal process you might see in a totalitarian state.
Without the Sixth Amendment protections, police or other agents of the state would be able to detain citizens and visitors without charging them of a crime, charge them without evidence or a fair trial, or charge and detain them without ever trying them. These are the practices of a totalitarian state.
The Sixth Amendment guaranteed what we call "due process of law." It was observed in the breach for much of our history, and we still test its limits, but it is central to how we perceive our government. You can't be detained without a fair trial indefinitely.
If such a detention occurs, a lawyer can petition the government to release the person detained (with a writ of habeas corpus) because of this limitation on government power.