Is a Spell Checker another name for a Wizard?

So spell checking. Can anyone tell me why this isn't done natively in the operating system as you type. Think about it. Whenever you type on your computer - the operating system - not the application - should natively spell check what you write. Why have all of this redundancy in applications that spell check within the application? My operating system should simply be checking everything as I go....

Someone tell Microsoft and Apple for me.

Ace