If you really want to know why you use iTunes to sync so much non music stuff, the answer has to do with history and evolution.
In the beginning, there was iTunes, which stored and played your music for you. Next came the ipod, a music-playing device, and it seemed only natural for Apple to use iTunes as the software that moved music from your computer to that device. Also, because the ipod had a screen that could display text, Apple provided – just as an extra- special bonus – the ability to copy contacts and calendars from your computer to your ipod so that you could have them with you as you walked around listening to your music.
But the ipod soon developed more capabilities, such as the ability to show video, so Apple added video playback to iTunes and enabled iTunes to share that video with the ipod.
Then came the iphone, which was like an ipod from the future: It could not only play music and video and display text, but also hadle email, create appointments and contacts and calendars and apps and bookmarks between the iPhone and the computer.
After that came the iPad, which can hadle even more kinds of information, and Apple grafted the ability to sync those kinds of information onto iTunes as well.
That’s where we are today, with the distant descendant of the original music – playing application managing all sorts of information on the descendant of the original handheld music – playing decive: evolution and intelligent design joining hands, wearing white earbuds, and dancing together. We get all misty just thinking about it.