Most fields don't reformat and add characters like spaces as I type. I personally find it a bit jarring. I suppose reformatting it one the box loses focus isn't as bad, but I'd still prefer you just keep what I type.
The iPhone reformats phone numbers as you type them, and I personally don't find it jarring at all.
Try moving to a country that splits phone numbers different that what you are used to. I grew up with 3-3-4 but live in a country that splits 2-4-4. Subtly annoying.