Some of the services I pay via Apple's subscription workflow is cheaper. Unbelievable, but true. Pocket is one, Evernote is other. However, they later synchronized their pricing to be cheaper everywhere, but it doesn't matter. It makes my life easier.

If I'm paying for a cross-platform service, I can happily use their own methods, but if I'm paying for an app-store only application which either runs only on iOS or macOS, good luck to them. I won't subscribe via their methods, because it makes my life more complicated.