It is probably due to many users having removed icons accidentally and not knowing how to get them back and fearing they have deleted the application or folder or whatever. Just take a look at those "deleted icon from dock" threads.
Anyway, you can also just hold down the CMD key while dragging off the icon from the Dock to remove it from there. Apple did the same with the Sidebar and in of the 10.6.x updates, removing the ability to remove a Sidebar item by simply dragging them off. Now you also have to hold down the CMD key for this.
Mac OS X, or OS X nowadays, is aimed at consumers, most often ones, who don't understand one iota about computers and how to use them. Strange, as it would be really simple to include simple video tutorials with their OS, but not even Microsoft does that, so why should Apple? At least they have their website with some simple tutorials, but one has to look for it, as there is not even a Safari bookmark for that. Dumbing down, the new fear.
