I'm only saying it isn't the only approach, even if you're keeping the source of truth in memory. It's the most prescriptive approach for sure so is the one people tend to go for first but there be dragons in managing especially long lived journals. Migrating the journal over time, figuring out how to truncate it (especially if there is an initial creation command/event that describes the rest of the life, or periodic updates to the structure - you have to keep all of that data forever potentially to know that it's going to wind up being correct.)
And yes long recovery times are an issue unless you want to keep every entity in memory forever and ever, or you can tolerate extremely slow turnaround times. There are knobs and dials here that are subtleties that people won't think about until after they launch.
If you have a hammer everything looks like a nail kind of thing. There are other ways to handle problems that are only marginally different in how they persist and recover state, yet are far more usable for certain use cases.
I'm extremely skeptical when I see someone gung-ho for event sourcing if they've never used it though. I tend to look at the problem very hard to see what else we could do for persistence while still maintaining the "source of truth" in memory.