In the same way USD is backed by faith in the US government, BTC is backed by faith in the Bitcoin miners. If either loses credibility, the currency goes to zero.
What Is Bitcoin Backed By?
People often say: “bitcoin can’t be money, it isn't backed by anything.” This is an old way of thinking that originated with paper money. Prior to paper money, people used precious metal coins (such as gold) because they maintained strong monetary properties: scarcity, durability, divisibility, portability, fungibility, and acceptability (the six monetary properties). Paper became money because it was superior to gold in terms of divisibility and portability BUT it lacked scarcity. People reasoned that we could benefit from the greater divisibility/portability of paper money as long as it was redeemable in a ... (full story)