However, there is just more going on in an event sourcing model. Instead of saving data to a location and retrieving it from that location you save data to one location, read it from another location, and you need to implement some sort of linker between the two (or more).
This also comes down to my personal subjective experience. I actually really like event sourcing but I have worked on teams with these systems and I have found that the majority of people find them much harder to reason about than traditional databases.
(declare-depot setup *my-events (hash-by :user-id))
That's it, and you can make as many of those as you want. And here's how a topology (a streaming computation that materializes indexes based on depots) subscribes to that depot:
(source> my-events :> *data)
If you want to subscribe to more depots in the topology, then it's just another source> call.
That these are integrated and colocated also means the performance is excellent.
Seeing Closure ironically makes me think of Twitter though.