i have no idea why a small amount of inflation is considered ideal

Because it encourages money to participate in the economy. If an economy gets stuck in a deflationary cycle, it encourages people to stop putting their money into the economy to invest or to act as a way to get people to make purchases sooner.

That can be ideal if you are anticonsumption, but not so much if you are relying on a low unemployment rate to help keep people happy.