There are three major reasons for blockchain got a head start in finance and that blockchain companies are targeting the financial sector:
1) Because Bitcoin is a financial instrument it was more obvious for financial services to first examine ways to use blockchain technology than, for example, for healthcare or other areas outside of finance to imagine how to leverage blockchain.
2) The prize is great. Financial services is an absolutely massive sector and any disruptive technology introduced into finance creates significant opportunities.
3) Financial services arguably has not been as heavily impacted by the internet and other recent technologies as, say, the media or other sectors that have been transformed by the internet revolution. Blockchain has also served as a ‘focal point’ for the much needed modernization of financial services, which has been protected a bit behind a regulatory layer that prevents certain technologies or companies from changing the status quo.
Garrick Hileman and Michel Rauchs released the 2017 Global Blockchain Benchmarking Study, which can be downloaded as a PDF here: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3040224.
You can read the brief summary of their study here: https://insight.jbs.cam.ac.uk/2017/central-banks-are-trialling-blockchain/
The above interview was conducted on 12 December, 2017.