I don't think this is true (game consoles notwithstanding). Throughout history, there have been but a few mediums in use at a single time. Most of the time, all these platforms were supported. (Now, it's any number of content distributers on the web, DVD/CD and Blu Ray. 10 years ago, it was DVD and VHS.) The notion of products bound to a specific platform or medium rose primarily with the popularization of consumer computing, and software likely remains the most platform-specific content available.
Wasn't this why the internet was invented, to disseminate information in a platform agnostic fashion?
Being an app is just to provide a revenue source; if it was a web blog then it would be open to everyone for free. This is the free market at work, if you prefer free blogs then don't pay for it, if you want to pay for content that is very likely found elsewhere for free then the convenience is there in the app. It's the curation that you're paying for.
I hid newstand because I believe that everything I ever could possibly want to read is on the internet for free anyway.
The Internet is an underlying communications platform that was intended to be a set of robust, fault-tolerant, and distributed computer networks.
The WWW is specifically the intersection of HTML (markup) and HTTP (transport protocol) for document sharing over an underlying network protocol (generally TCP/IP on the Internet).
