The core purpose of using blockchain technology in cryptocurrencies is to provide a decentralized, secure, and transparent ledger for transactions. It eliminates the need for intermediaries, allowing peer-to-peer transactions to be conducted directly. Each transaction is recorded in a block and linked to previous blocks in a chain, ensuring authenticity and integrity. This structure helps prevent fraud and double spending, creating trust among users. Additionally, blockchain technology promotes transparency, as all transactions can be verified and audited publicly.