Starcraft – How to set auto-casting using hotkeys

If you go to options, hotkeys you can assign it to whatever you want. It is called camera-save. By default though some menus take up f9 - f12, so ctrl+f8 is the only one that works for camera saving with the default profile. You either need to pick different keys or take the menus off of those hotkeys to get the other ones to work.

I would argue that if you're just starting out, grid hotkeys are more efficient since you can memorize either which key it is or where on the unit-card the button is located (visual cues tend to help memorization) - and if you don't know the hotkey, you can find it without mousing over the button.
Also, all the keys are on one side of the keyboard, meaning you won't have to move your hand as much.

That being said, the vast majority of players use the default keys either because
A) They don't know grid exists, or
B) They are already used to the default layout (grid was not an option in the beta), and/or were already used to the very similar layout of Starcraft 1; there really is no benefit to them learning a new layout if they already have the default hotkeys memorized. Most competitive players would fall into this category.