Crypto's early promise rested on radical transparency. That design gave blockchains their auditability, but it also created a problem the industry has never solved: most people don't want every payment, salary transfer, donation, or business transaction visible forever. Privacy coins emerged from that discomfort. They promised something close to digital cash on public rails. Users could transact without exposing their full financial lives to a ledger, an analytics firm, or a future adversary.