Throughout history, governments have gotten themselves into trouble by spending more than they have. When the gaps become too big, difficult choices arise.
One option is for the government to increase revenue by raising taxes. This path is never popular with citizens, and in a democracy is hard to push through. Even in authoritarian states (where there are no pesky elections), tax increases are problematic. Higher rates always discourage productivity and deflate economic vitality. There is a limit to how high taxes can go. Raise them enough, and people stop working. Raise them higher, and they may even start rioting.
A far better option is to cut government spending. However, this is often more difficult than raising taxes. Those whose benefits are cut are particularly apt to express their hostility both at the polls and on the street. This is especially true when the recipients feel entitled to the benefits. Politicians make lots of promises to secure their elections and voters rarely consider the ability of taxpayers to actually foot the bills.
To avoid either of these politically unpopular options, some governments choose to default instead. In this option a country simply tells its creditors that it can't pay the full amount of its debt obligations. If the debt is largely owed to foreigners, the decision is that much easier to make. Politically speaking, it is better to stiff a foreigner than to raise taxes on, or deny benefits to, a country's own citizens.
For political leaders, default can be rather embarrassing, as it amounts to an official acknowledgment of insolvency. To avoid this, many opt to simply print money to pay debts, effectively repudiating their obligations by inflating them away. Since inflation is usually the easiest choice to make, it is often the most likely. But while it may seem easy at first, it ultimately exacts the harshest toll.
Inflation allows governments to avoid hard choices and dispose of their debt on the sly. By printing money governments can nominally pay back all that they owe, but they do so by diluting their currency. Creditors get paid, but what they get isn't worth much, and if inflation turns into hyperinflation, it's worth nothing.
Inflation is simply a means to transfer wealth from anyone who has savings in a particular currency to anyone who has debt in the same currency. With hyperinflation, the value of savings gets completely wiped out and the burden of debt is removed. (Those who own hard assets do okay, because, unlike savings in currency, assets will rise in nominal value when inflation flares up.)
— Peter Schiff; How an Economy Grows and Why It Crashes