In my experience, lots of banking, some trading. In both cases, it is used for history, audit and precision.

The idea is that for banking, it is not enough to just get the _current_ state - the more important thing is how someone _reached_ that state.

Adding history to transactions is not new - so rather than bolting on a history/audit mechanism, you knock out both - a higher resilience, distributed system + built-in audit/history mechanism.