I doubt attacking humans would be good for orcas in the long run, and perhaps their intellect allows them to generally understand this while sharks don't. (Orcas don't even nibble on humans out of curiosity, so how would they know we don't taste delicious? In this regard sharks seem more curious than orcas, which is seems strange since they're otherwise very curious animals.)
There are no known attacks on humans, that doesn't mean that is hasn't happened. Orcas are generally not hunting where humans swim, and they aren't going to capsize a freighter. Plus there's better food in the water, and it's more frequent. An orca, or a family of orcas that would specialize on hunting humans would starve. We don't swim in the open sea a lot, they don't walk through towns a lot.
I believe you're over-estimating their intelligence.
> I believe you're over-estimating their intelligence.
One of my favourite orca stories is the killers of Eden[0]. The wiki page is short and worth a read, but to summarize: a pod of whales learns to herd whales into a bay and alert humans to them. Humans harpoon them and the pod helps drag them back by pulling on the ropes. The carcass is left overnight for the pod, that eats its lips and tongue. Afterwards, the humans haul it back.
Why would the orcas alert the humans unless they realized that the humans were responsible for the harpooning? Furthermore, just the act of slapping the river with water to attract attention is already quite advanced. And why did they only eat part of the whale (and always the same part)? Why did they never eat the humans?
[0] https://en.wikipedia.org/wiki/Killer_whales_of_Eden,_New_Sou...
I don't believe they're "if you eat that guy over there, the navy will come and hunt us down" smart though.
Since manual whaling hasn't happened for quite a while, they'd need to communicate abstract concepts to their offspring to keep the memory alive. It's one thing to demonstrate to them how to synchronize dives to create a wave and flush a seal off of an ice sheet, it's quite another to explain the process of humans hunting them with ships and harpoons and indicating that humanity's technology has progressed.
Think about how you feel approaching a very large animal, like a horse you don't know. You don't need to know how or even if it can hurt you, but it's worth being careful. If you know the animal has sharp points (like a large dog), even more so. I think sparrows avoid cars by similar logic.
I really think non-verbal, subconscious intelligence is capable of a lot more abstraction than people think. We need language to describe it, but not to do it. "Threat" is an abstraction that lots of simple animals handle just fine. It's not so much that we need to give animals more credit than that we give ourselves too much. Our actual motivations are usually much simpler than the stories we tell ourselves.
What's really interesting here is the problem of just a "naive threat estimation", which usually is always just estimating the purely mechanical danger the body of a foe could pose. We have a healthy respect for large animals like horses and cattle that could crush us. We've got an open fear of predators with obvious sharp teeth and such (wolves, big cats, crocodilians). But bugs? Bugs are really weird because they're not mechanically dangerous, and as, say, a child, sizing them up, there's no sensible reason to be scared.
I find it really interesting how - even without necessarily understanding that they've got poison, we as a species do a really good job of being scared of "things that aren't visually obvious threats" like this - especially in kids, who really struggle to "get it" when it comes to what's actually dangerous about, say, a spider or a jellyfish.
I think you really hit on something there - I think a little bit of it is actually a built-in instinctual fear, but there's also a huge part that's an imitative fear kids pick up from anything that the body language of a parent conveys as dangerous.
See, something insects don't get.
> "I’ve seen them look at boats hauling fish. I think they know that humans are somehow related to the scarcity of food"
If they are really that smart, they would be smart enough to figure out humans are made of food too, right? Some orca at some point in time would've realized it and eaten a human, yet that hasn't happened.
Hear me out: what if they don't kill us out of self preservation? They see the fishing boats, the harpoons. They even see the gigantic war ships, and are probably smart enough to realize that those are linked. Would we attract the ire of a species that is much more advanced than ours if it was just harvesting resources? Not until we're almost dead from starvation.