I assume the parent is referring to the problem where it's prohibitively expensive (from a payment processing perspective) to receive lots of small, sub-dollar payments.
Also there's a lot of friction if you're relying on your users to pull out their credit card info for such a small amount.
Actually no, sorry for the lack of clarity. I was thinking more of the administrative problem for the consumer.
Like, I read a lot of news, and every news outlet I read would like me to subscribe. But while I do have couple of subscriptions, and if I was a bit better off I'd throw down for a few more, but if I were to buy a subscription to every outlet that I read 1 or more articles a month from then not only would it get expensive, it would generate an annoyingly large number of renewable transactions. I don't want 30 different subscriptions, especially when I might read a publication frequently for several months and then take a break from it for a similar period. I really like the journalism at The Atlantic for example but I haven't gone to their website for maybe 6 months; in this febrile political climate I've been reading more instant news and a bit less analysis/longitudinal work.
As you say I don't much care to pull out the credit card for a small amount, but I'll make smallish one-off purchases when I find something cool. What I'd like would be that I pay some fixed amount like $25/month and someone else takes care of distributing it approximately proportionate to where I spent my attention.
When book/magazine stores were more popular I used to buy a lot of magazines because I could go to one place and get a wide variety but not necessarily always the same ones every month. But it was only one or two financial transactions with a single vendor, the magazine store. This was more expensive than subscriptions, but more flexible plus I didn't get nearly as much junk mail. I hate marketing and when you buy magazine subscriptions you get swamped with it.
That part has been fixed by https://flattr.com/ You either prepay or setup a periodic payment and then just click the flattr badges whenever you want. They get funded from your flattr pool. No need for the card every time.
The problem as stated was: "it's prohibitively expensive (from a payment processing perspective) to receive lots of small, sub-dollar payments", and "a lot of friction if you're relying on your users to pull out their credit card info for such a small amount".
These are solved. User adoption is a completely different issue that applies to almost all donation systems. Even if nobody uses X, it doesn't mean X doesn't exits.
You missed the parent's point which is that just because a product exists, doesn't mean a the problem it addresses is solved in practice. Even a very good solution needs to be known about, readily available, priced correctly, and not suppressed by other forces, as well as extant.
Also there's a lot of friction if you're relying on your users to pull out their credit card info for such a small amount.