You could say that blockchain isn't really "necessary" in any field at all. If you think about it, most, if not all, fields were getting along fine before blockchain came along. However, this is not to say that there aren't practical or useful applications of the technology, that make different aspects of life/society/etc. better. For example, blockchain technology can be used for smart contracts, transparency in supply chains, fraud-free elections, and of course financial things such as cryptocurrencies and decentralized exchanges.