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.
Blockchain technology really not that necessary for any field unless you want to make a radical change for the betterment of that field and the people who are involved with it because like blockchain in bad hands can do many harm in good hand it can do miracles and I know this because I have involved with so many ICO programs related to health care sector which are specially dedicated to develop health data management and other essential tasks in order to treat patients in a better way which is some thing was doing without blockchain technology in the past but such progress was possible in a short period was thanks to blockchain technology . So yes blockchain technology is not essential for any field but to develop and do miracles blockchain technology can help us immensely