Cause it is not YT or only fans, where it can be monetized by ads. Mangago has changed their terms&conditions after Pian Pian case which caused website almost get down. Now it has almost no ads monetization, only external ads monetization which is still not bad for the owners of website, since it is currently one of the biggest visited websites out of all illegal websites due to it not having ads, pop ups and glitches for those who have accounts.
Authors are bonded by contracts where the right for their work partially belongs to official websites. Le//in and Ta!@s hold the exclusivity of the webcomics which makes webcomics to be uploaded only on those official platforms. For which platforms earn most as well as creators can have constant income + profit from every bought chapter that users spend money.
You dont watch Netflix shows on YT just because shows can earn extra money by YT monetizarion, no it doesn't work like that. Netflix buys the right for the material they release which makes it exclusive for it and since people can watch it only on Netflix so they will go watch it on Netflix but not in any other place.
Why dont mangago provide some profits made by the website so even authors are happy and all readers, uploaders are happy too ╥﹏╥