>As is often the case with tech companies, new business models, like tipping in this case, play on ancient ideas and practices, but make them many orders of magnitude more accessible and scalable through software.

The scale is the very thing that kills this model. With a small, close community, there is huge societal pressure to live up to your obligations, and not doing so has huge social costs to you (you become isolated from your community). At Internet scale, you no longer have the community to enforce social norms, and not living up to your obligations may actually be lauded in r/lifehacks.

I experimented with this when I first launched my startup. But what I found is that it torpedoed our ability to sell to institutions. Universities would just tell students to go get it and not pay for it. And governmental organizations said they couldn't opt in to paying for something that they were allowed to take for free. It's too bad, because we were able to serve so many more people through that model, but organizations that are happy to pay now simply wouldn't contribute back then.

Maybe what we need to do is have a list price but then give out free coupons like crazy?

The inca empire was built on this business model. However on the internet you'd need to do a bit of a foundation shift to make it work (which is incidentally what I am working on).