What is the advantage of the state government making laws for the people?

Yeah what she said on the bottom

Some advantages:

The Constitution protects the rights of minorities against the tyranny of the majorityFree speech and a free press are protected especially in the cases of public figures and political speech (eg what might be libelous against a private person is often allowed against politicians) The Establishment clause of the Constitution prevents religious doctrine or laws from being imposed by the governmentThe separation of powers prevents the government from becoming too powerful or acting too rashlyThe autonomy of states and local jurisdictions allows issues to be handled at the lowest appropriate level, presumably allowing different results for different regionsThe Commerce clause of the Constitution makes the USA an enormous free trade area (contrast with India where states and impose tariffs on products crossing state borders).

Some Disadvantages:

The separation of powers can delay or stop government action on important issues, especially when the president and congress are controlled by different parties. Some of the powers granted to states create wasteful inefficiencies, eg, regulation of insurance companies and medical care by states rather than having one national standardSpecial interests have disproportionate influence with the government; financial contributions are not sufficiently transparent In most states, incumbent politicians have too much influence over which voters are included in their districts