Originally, the US Bill of Rights did not apply at the state level; only the federal level. For instance, the right for a criminal to be represented by counsel, granted by the 6th Amendment, did not originally apply to state level criminals.
The process of incorporation of the Bill of Rights reversed this and made these rights apply to state level. But why wasn't it this way to begin with? What was the original rationale to have the Bill of Rights only apply to the federal level?