Answer: Power can control and abuse the citizens too much. Tax would start to rise.
As Thomas Jefferson stated; “That government is best which governs least...” The idea that it’s bad for a government to have too much power, came from the anti federalists (republicans) . The intent of separation of powers is to prevent the concentration of unchecked power and to provide for checks and balances, in which the powers of one branch of government is limited by the powers of another branch—to prevent abuses of power and avoid autocracy.