> Just how many millions of people do those outdoors activities?

Many, but that's irrelevant. There are hundreds of thousand of bicycles in my city, and very, very of them have cameras. That's kinda the point: what you're selling is the dream of being a YouTube influencer, pretty much. Otherwise, there's little value to having a big library of videos from every ride you've taken, especially since let's face it, most people ride the same routes / trails most of the time.

Now, the dream of being an influencer may be a strong selling point, but you can only do it once. People are not gonna keep upgrading.