The 120 degree FOV makes it seem like they're sprinting while the 40 degree FOV looks like a slow walk in comparison. Also pay attention to the little box the person walks past halfway through the below video. Imagine you're skateboarding and that is a parked car. The difference in speed and perceived danger is huge.
I think you are on to something with the amount of stimulus though. I ride a One Wheel which... has one wheel, and the nearer I get to top speed the less speed it has to balance me.
The sensation is different. The wind is blowing harder on my face, I have to scan and process each ridge and change in the road, my balance is different, is that car opening it's door? is it going to turn, that drain cover is bad need to lean to avoid it, car behind me can't go left, does my front foot have too much force, intersection coming up slow down, speed up no cars, turn signal are they going to cut my lane... etc.
Meanwhile if I'm sitting in a car, well... 20mph is nothing, I'd barely notice it. The wind sensation is gone, I'll go straight if I don't touch anything, people respect my area since I weigh 2000 plus pounds.
The perspective is different, the level of sensation is different. It's similar how a go kart feels a lot different then a car in regards to speed despite the fact both are four wheeled motorized vehicles.
Who cares about the random video you took down a mountain, it's fun in the moment and no one can take that away from you. To an external observer though, why should that be interesting?
The lack of speed is one thing, the lack of context is another. They don't know about the ice patch you're watching out for, the sensation you get when you hit the powder just right, or even that you are going 10% faster then normal (sorry I'm a blue square skier and don't really know what goes through the head of people who are actually good).
Drones and helmet cams actually seem like they have pretty niche applications when an iPhone will do great for 95% of people, 95% of the time. The need for that particular lens and shot just isn't usually called for in whatever you're trying to create.