Have you considered that when you were a kid you would have been too clueless to notice them and when you're an adult they would be not very likely to out themselves to you?
You're likely not playing the same games they would be either if the target audience of what they're lurking in is aimed at children.
I don't think making all humans high-viz is the same as making everything high-viz
With that said, it would make a lot more sense to just enforce more training and license requirements on driver's. And set size limits on vehicles so they can all actually see what's in front of them.