Even if someone was able to attract the size of the audience required to make such a move possible, over time, people would grow wary of subscribing to yet another publication, entering payment information for it, etc.
Mind the Clap
M.G. Siegler

While in Medium’s economy model, subscription helps in reducing the friction in payment, centralized payment is not a solution for attracting subscribers. It doesn’t help content creators attract new consumers even if consumers don’t need to subscribe to the creators separately.