The "web" as in Tim Berners-Lee(TBL) "world wide web" is http+html which is "documents".
Saying TBL-web is "best as a document platform" makes perfect sense. It was defined that way therefore, use it that way. It's tautology.
Back in 1993, if we want to say "X is best though of as a network app platform" we'd have to use the word "internet" instead of "web" for "X" to be conceptually pure and technically correct (the best kind of correct.).
But now we have things like Dropbox (and thousands of other "web apps"). Dropbox runs on "http".
Dropbox "syncs". Syncing is an app. Dropbox is an app. Dropbox runs on http. Http is "the web". Apps run on the web. The web is platform for apps. That's the reality of where we are today.
Dropbox without using http_port_80 would only work in a laboratory. One big reason Dropbox is valued at $1+ billion dollars is that it uses http so everyone can use it easily. Web browsers didn't require radical changes. Corporate firewall rules didn't have to change. That's how they got quick adoption and millions of users.
