The upper classes, who obviously have all of the economic power, have designed it this way in order to prevent the formation of a new class that could threaten their position. The best (legitimate) way to gain wealth from nothing is to work hard and to save and invest the money you make so that it will grow. The purpose of continual inflation is to continuously undermine that process.
The best way to think about inflation is direct theft of your assets by the class that creates money (and thereby causes the inflation). If they print enough money to cause 15% inflation, then in effect they have stolen 15% of all assets from the lower classes. They themselves (as a class) are not effected as badly because they are, of course, the primary beneficiaries of all the printed money, and are adept at preserving assets across generations.
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