It’s a good question. Although, technically, shares are not valuable. Traffic from shares is valuable. But both are pretty easy to game. And if we were to start paying out on them, we would have to fight that gaming.
Less gameable would be subscriptions, to your point: “If I’m writing behind a paywall, I’m not just creating premium value to exclusive readers, I’m literally bringing new subs to Medium, and that as an author (or social media influencer) would be something that I’d appreciate being rewarded for.”
We’ve done some experiments with referral fees for writers. They weren’t encouraging. I think because most writers — or at least those we were testing with — weren’t that interested in marketing themselves (or Medium), nor particularly good at it.
It’s also tricky because the way the meter works, most people, even if they come from outside, will read your paywalled story for free. If they happened to be at their limit and convert on your story, that’s valuable. But should we pay just for that one or all of the metered views leading up to it?
Another thing to think about is that, if we were to do this, it doesn’t create more money for writers. We’d have to take that from the budget we’re paying out already.
It’s all about rewarding the right thing. If we reduced the amount we paid for making subscribers happy and routed that amount to bringing in traffic, I’m guessing we might increase traffic but lower quality.