Subscribing to one is easier than subscribing to many. There is less friction and the user gets more for that subscription.
> Why does subscribing to one developer give access to all developers?
All developers (and everyone else) can add subscription checks to whatever they like that will let only subscribers pass.
> Why not put yourself in the middle and offer a subscription to "1Sub.dev" and give users the same benefits?
Then they would all have to pay me. I don't want that. Someone could have something against paying me. Maybe the payment methods I offer doesn't work for someone. Distributing payments seems like the only right thing to do.
> What does it mean to "give access to downloads and other resources"? What kind of downloads and resources?
It could be anything. Here is an example of a paywall for this comments page that will only let subscribers follow the link:
https://1sub.dev/link?u=https://news.ycombinator.com/item?id%3D&s=p_GonuAYEe0&k=&n=hK5ZOXymlHi5s2Es&a=a.18
> Can you give some examples of services that exist that you think don't work well enough?I don't know what kind of services you mean.