Because inflation applies to both the amounts you owe and the ammounts you save. It’s kinda baffling to see multiple people here arguing that inflation encourages hoarding or not spending. Specifically it does the opposite. Money you save loses value, so you need to invest in something that returns value faster than inflation rather than sit on a pile of cash. Money you borrow also loses value, so the money you pay back later is less than the amount you borrowed. If you pay the same amount each month for your mortgage for 25 years and inflation is 2% each year the last payment should be half as valuable as the first (edit: about two thirds, actually. Maths!), so you’re encouraged to buy on credit.

More importantly, governments have tools to control inflation, so they can intervene and course correct when sudden imbalances happen. The anarchocapitalist fantasy where the market balances itself is extremely dumb, government intervention is absolutely needed, and tools to regulate runaway effects are what keeps all your savings from evaporating every so often.