Printing money doesn't create value, and value is what is actually traded in the marketplace. Money is suppose to represent value, and value can only be truly created through a mix of cleverness and effort. Value is what determines demand (what is valuable for people) and thus we someone can supply that demand (which is where we get production).
Printing money doesn't create value.
Value creates production.
Thus printing money doesn't create production.
And this is fundamentally why we shouldn't print money, because it doesn't produce anything. You could argue money itself has demand since it is suppose to represent value and so it actually has value, but like all things this demand is limited. Sure, for now everyone wants money. But once everyone in the United States owns a million dollars will they see the same value in just one dollar as they did when they owned only a thousand? Unlike other things, the demand for money could easily be met and everyone could have all the money they want. The paradox here is that once we fulfill this need then the money becomes useless because its lots its ability to represent value. Its value is directly propositional to its supply.
Say someone wants bread so they won't starve. Each piece of bread is seen as precious and so it is well protected. If they where suddenly handed 100 loaves of bread, they would eat till they get full and wouldn't care if someone comes up to them and takes just one slice. Their perception of value for that one slice of bread changed with availability. Inflation results from this change. In order to get the same value for something that they previously traded for 3 slices of bread, they must now get 6 slices or else it isn't worth it to them to trade at all since people are just giving them bread. If it rained bread from the sky, they probably wouldn't bother to trade for it at all. This is called hyperinflaton where what was previously traded with becomes useless.
In this case it would actually be good, since no one would have to go hungry. But in reality, the money we use has very little value since it cannot be eaten.