I would imagine there are a few differences. Events are the primary entity, and the current state is simply a projection of that not the other way around. Those events may come from other systems and are often defined in business terms, not SQL terms. For example an event may also constitute a business update which can update one or many tables. Think of a transaction event updating a balance for two accounts.

TL;DR My thinking it allows you to capture more the intent of that event. Although I'm not sure you need an immutable database to do this from scratch - I've seen this in schema designs in the past?