The Internet is mostly and primarily a communication tool.
Its importance of content delivery is clear and movies, e-books, music, found the right, fast and economical way to be delivered.
Content is what makes the Internet so precious in ordinary life.
But the killer application was and still is "emailing".
What is the first thing I do every morning after booting my computer and the last I do in the evening?
It is checking my email folder.
The same can be said when it comes to cell phones.
The "personal" use is by far the most common application.
A cell phone is first and mostly a phone.