Is a Cryptocurrency necessary when using a blockchain?

Cryptocurrency is not always necessary when using blockchain technology. While cryptocurrencies were the first and most well-known application of blockchain, the technology has since been applied to a wide range of use cases, many of which do not involve cryptocurrencies at all.
Cryptocurrencies are often used in blockchain applications as a means of exchange and store of value. For example, in a decentralized application, users may use a cryptocurrency to pay for services or goods within the application. In some cases, a cryptocurrency may also be used to incentivize users to participate in the network, such as in a proof-of-work or proof-of-stake consensus algorithm.
However, there are many other use cases for blockchain that do not involve cryptocurrencies, such as supply chain management, identity management, voting systems, and asset tracking. In these cases, blockchain is used to create a secure and transparent system for managing data and digital assets, without the need for a cryptocurrency.
So, whether or not cryptocurrency is necessary when using blockchain will depend on the specific use case and the problem that is trying to be solved. Cryptocurrency may be necessary if the use case involves transactions and requires a means of exchange or store of value, but it is not a requirement for all blockchain applications.