Why has the power to regulate interstate commerce become such an important power of congress?

The Constitution defines what the federal government can do. This is supposedly all that the federal government can do. All else is left to the states to govern themselves. For example, the original purpose of the federal government was to wage war if necessary to protect the people in the states - it was all about the people.

The federal government has found two ways to intrude into the freedoms guarranteed tot he people by the Constitution.

1. The federal government issues mandates for the states to follow. If the states don't do it, the fed cuts off money used for mutual benefit, such as highway funds. Keep in mind that all money in the USA comes from the people's taxes - so the fed threatens to refuse to use the money taken from the people to benefit the people in any state that refuses to go along.

2. The federal government is allowed to regulate interstate commerce, just as the FBI is allowed to investigate interstate crime, but not crime within a state. Lately the congress and the fed have sought to re-define what interstate commerce is in order to gain more power over, and take freedom from, the people.

Obamacare is an example. Explanation of Obamacare: You go into a 7-11 store. The clerk asks you, "do you want to buy a coke ?". You say "No, thanks". Then the clerk says, "That will be 10 cents tax. Please pay me or I will call a federal marshall !". Is this interstate commerce? Has freedom beed taken ?