;) Not just that, but, for example, If I have variables x, y, xDir, and yDir, and I type 'x' and press TAB, which variable is selected? Ambiguity ensues! ;)
Edit: Just to add to my first post, another reasoning is because commonly I type the first 2-3 letters to single out a specific group of variables (I may have tons in a game), and if I type a wrong char by mistake, I lose the code completion pop-up and have to back up and retype the period! :/ Anyhow, glad it's on the to-do list! :D