Why is it important for only Congress to print and coin money?

People are constantly asking the government to spend more money on them, in the form of welfare, social security, etc, without raising the taxes. The best means of doing so is to create inflation. Economists have noted that the highest increase of inflation can be about 5% before the public catches on a panics. In the US, the inflation rate is about 2.5%.

One other issue the government has to take into consideration is the debt. To pay off the ever-increasing debt, congress coins that money.