To solve this problem, governments destroy their fiat currency in order to pay their debts. They print a lot of Money and end up generating a lot of inflation: inflation is seeing the purchasing power of your money decreasing. If you print more money, it makes it less valuable. It's the famous law of "supply and demand".
Knowing this, just look at the Dollar: in the old days, 60 years ago, when it was still backed by Gold, this state currency had a lot of value, as it was scarce and depended on the amount of gold the government had in its reserves; but in 1971, American President Dixon, removed that "need".
Knowing this, we can see one of the biggest strengths of Bitcoin: a decentralized cryptocurrency that does not depend on any government! Its network is distributed worldwide and is not subject to presidential or dictatorial policies.
Also, another very strong point of btc is that, in its schedule, there can only be 21 million units to be mined; this ends up generating long-term deflation, not inflation that governments love so much! It didn't exist until then.
Some economists project the Bitcoin price 15 years from now at $2,500,000.