Simulpub is getting more and more popular. Some manga even got a simulpub before fan translation. But the problem is they're way too scattered. Forget about the cost for now, it's physically and mentally exhausting to keep track of all the manga available out there. There's no convenient way to read them all.
Monetization is also a complete nightmare if you want to read a lot of manga. Mangaplus and Azuki have subscription-based model, but others like K-Manga (Kodansha), Mangaup (Square Enix) and Comikey still use the archaic system that's used in Japan: the COIN system that we all hate. And there are over 100 minor manga publishers out there with no access to the global market yet. Even if they do have access, how much would it cost for a person to subscribe to them all?
You need around $45 a month to watch ALL seasonal anime legally, but it even possible to have a super library for legal manga? let alone making it user-friendly with affordable cost & ease of access (no region locking). Even in the H industry, the mighty Fakku only partnered up with Wani and no other publication.