As consoles get more powerful locally, that stuff happens locally. Again, Uncharted 3 had huge storm waves and disappearing vessels. That affect on gameplay you talk about doesn't require the cloud. Cloud needs a role that requires many teraflops, making it stand head-and-shoulders above what a console can do, if it's to have a presence in single player games.
The point here is that everyone see's the same thing happen. If the waves were modeled on each individual machine then not everyone would see the same thing. If you attempted to have all machines sync with each other that increases the latency relative to the server solution.
In Sea of Thieves, this is important as waves + horizon effect affects both the ability to see the enemy as well as where cannons will impact the enemy. If everyone wasn't seeing the same thing then modeling where cannonballs hit would vary from player to player. Same with seeing and reacting to the other ship.
The ship to ship combat as it exists in Sea of Thieves right now would be different if each machine rendered and physically modeled it's own waves. If nothing else it provides consistency. Nothing annoys me more in a game with other players than for me to call out something cool that I just saw, only their machine didn't render what I saw and rendered something else instead. One example I can think of immediately is pets (minions) in FFXIV. Minions are all rendered and animated client side. The only serverside communication WRT to minions is that one exists and is attached to player X. So when they do something cute, it is highly unlikely that it'll also be happening on another players screen.
Now-a-days enemy locations are generally synched as that's important. IMO, having environmental effects that visually affects what is going on be synced is the next big step in immersion. Especially as that means it can no be an integral part of gameplay. Having the ocean be sync'd among players is significantly more intensive than just syncing up a building falling (especially if the building destruction features a small set of canned animations as it is with virtually all games except Crackdown 3) as it allows player and ship positions to be synced and remain logical visually with the motion of the ocean.
As to your question earlier about single player games, it becomes a question of why not?
Let's use the ocean simulation from SOT as an example. Lets say a game has both a single player and multiplayer component. Why couldn't the ocean data be simulated for all players and shared among all players whether in a single player instance or multiplayer instance? The single player instance can just use the simulation data that has already been generated for multiplayer.
Unlike something like building destruction, why couldn't the server simulated ocean be shared among a great number of player whether single player or multiplayer? The ocean (including weather) can be the same in all worlds and instances, the only thing that changes is where players are. Unlike building destruction which is going to change depending on instance.
So in that sense, some forms of server side physics and modeling would be more conducive to cost effective use in single player games than others (world state versus object state).
It'd be interesting to see a cost breakdown. Looking at something like PUBG, everything is server side and everything must be tracked for all players across the entire map as well as any changes to world items due to player interaction. And that's just a low cost game without monthly fees. I'm not sure it's using that much less server timer per player than SOT. PUBG has to track persistent changes per match. SOT doesn't. It tracks things per player, but any changes to an island are basically reset after a short time. Quests will instance and populate an island with relevant items [treasure chests] which when found can trigger enemies to spawn, for example. Once that leg of the quest is done, the island is basically as it was before for anyone else to spawn a quest on it.
Regards,
SB