why does government print more money?

Voters want free stuff now! So if a government doesn't spend more than their income, other politicians that do so will get voted in, and the next government will overspend. Therefore governments tend to be in debt perpetually.

It's easier to print the money to get out of the consequences of that debt, than to govern well, create value and get out of debt that way.

It works up untill people think it won't work. A self-fulfilling proficy. (1)