Blockchain is just a database, a slow and expensive one at that. “Legacy” tech (like a RDBMS) is much more efficient, reliable, and cutting-edge than blockchain. The only benefit of a blockchain is censorship-resistance—not needing to rely on government or centralized third-parties because a swarm maintains consensus (the longest Merkle tree). Financial markets operate in broad daylight with real identities enforced by judges and men with guns. There is absolutely no use case for censorship-resistance in that space. It is a lose/lose. How is it even supposed to work? Bankers pay miners to secure a log of their transactions? Ok, say someone robs a bank. A banker calls in to report the loss; a block gets mined showing that money is lost. Why did you need a blockchain? Why not just trust the banker to update a RDBMS cluster since you're trusting the banker's word anyway? Blockchain only works for purely digital things...like Bitcoin.
Smart contracts also do not need censorship resistance. People get along fine with the current legal system at least for civil lawsuits.
You need a blockchain iff:
- The data you are representing are other data in the same tree, not entities outside the data structure (much less entities irl).
- You need censorship-resistance because you're Silk Road or Wikileaks or trying to overthrow your government.
- The data is publicly/www world accessible by parties who do not trust each other.
TL;DR A blockchain is a domain-specific data structure internal to the Bitcoin project circa 2009.