Governments don't really "print money" anymore, though in theory they could. They do complicated things with bonds that I'll let the monetary policy types explain in their answers. These complicated things fail in complicated ways, as Greece is right now.

If you expect the favorite demographic of our politicians -- "our children, and our children's children" -- to innovate faster than we are doing, you print more money (or issue new bonds). In other words, inflation is what you get when expectations rise faster than reality.

In practice, there are 6 major psychological reasons you might support borrowing against the future in a "rising expectations" way.

1. Genuine, informed optimism: you believe the future will create more wealth at an accelerating rate, based on beliefs about technological possibilities.
2. Uninformed optimism: you don't know how the numbers work, or have any fundamental reasons for having increasing expectations, but you have a general belief in "limitless human potential."
3. Looking out for your kids: you are actually pessimistic about the future, but you support borrowing against it anyway because you are in a good position to make sure your children and grandchildren are protected and positioned to milk the impoverished future better than their peers. You are enriching yourself and your descendants by robbing others' descendants basically. If you like the sound of this, look into things like living trusts, estate taxes and such.
4. Looking out for yourself: you don't have kids or you don't care about them (or anyone else's kids). You simply rob the future to pay for your present. This is kicking the tin can down the road. Or worse actually: like giving someone in the future cancer so you can buy an iPad today.
5. You are dumb enough that you think you can manage finances based on needs rather than capabilities. So you borrow against the future simply because you think certain entitlements are inalienable "rights" that cannot be cut.
6. You are not that dumb, but you cynically decide it's okay to rob the future to pay for entitlements you support on a preferential basis. This is a generalized version of reason 3 (you look out for your interest group's future -- often an ethnicity, religion or class-based group -- instead of your kids).

There is a fundamental and unprecedented condition in this discussion these days: the aging population and declining birth-rates worldwide. There may not be enough productive people in the future to rob.

If there are much fewer children or children's children on the horizon, unreasonable expectations get even more exaggerated, since the growth needed per capita to meet those expectations has to be higher. Either people start making more (and better educated) kids, or the Japanese have to develop those slave robots real quick. If neither happens, expect collapse basically.

I am not knowledgeable enough to fully connect the dots, but I don't think it is an accident that places like Greece and Italy are the closest to trouble: they have rapidly aging populations. They don't have the human or robotic raw material to grow themselves out of trouble.