Redux often does not have to keep track of versions, because the event stream is consistent for that session.
Downstream apps and consumers that don't need to be compatible with the entire timeline can then migrate code over time and only deal with the latest version. You have to deal with schemas anytime you have distributed communications anyway, but event sourcing provides a framework for explicit communication and this is one area where it can make things easier.
Why? Because a changing business requires changes to the Events. Since a change in an Event requires that all consumers to be updated, immediately or at the schema version deprecation, the cost of change seems to increase faster in comparison to an application landscape without event sourcing. At the same time, the cost to know who needs to be changed also grows since "any" application can consume any Event.
An stable application landscape also seems to be required because if the number of an Event consumer grows quickly the ability to update, and deprecated schemas, seems to be related with the number of Event consumers (which require update).
Sure. Events are like filled out forms, and there is a reason forms that are significant, modified over time, and where determining meaning from historical forms is a expected business need tend be versioned (often by form publication date). If you ever need to reconstruct/audit history (whatever your data model), you need a log of what happened when that faithfully matches what was recorded at the time, and you need definitions of the semantics as to how the aggregation of all that should map to a final state. Event sourcing is a pretty direct reification of that need, and, yes, versioning is part of what is needed to make that work.
Most distributed systems already do this, especially if they use Thrift/Protobuf etc. It's par for the course.
Its not that hard to deal with. Dealing with it through ad-hoc "we will come up with something as we go along" can be a bit of a pain though. It is in fact fairly trivial to handle if some thought is put into it.
It kinda sucks and there isn't a great answer. But there are a lot of use cases where there are real benefits to having that log go back to the start.
Better to "grow" your data structures than "change" them.