[leepowers]

* Not every keyboard has Page Up/Down keys. As an application designer you can't rely on their presence.

* The spacebar is the largest key. For an application, it makes sense to attach commonly used functionality to this key. For media players this is pause/play. For web browsers this is "scroll down a page", as you'll need to scroll down when viewing pretty much any web page.

[krizan]

Actually your answer makes the most sense. But It's confusing for the most users (people ARE the creatures of habits after all) I'm a business owner and customers asked me: "Why i can't do the same thing i do in VLC player!?" So i was curious.