You still have to mess around with a bunch of spaces when you're editing or copy/pasting, and not having exact even numbers makes for ambiguous situations.
Especially if something is 5 levels deep, it's really hard to see if you have 12 or 11 spaces (so 5 levels + 1 space or 6 levels) indentation.
My editor, I press tab once and it inserts the correct number of spaces (on a new line it also starts at the previous indentation level as appropriate). I press backspace once and it deletes the correct number of spaces.
Any editor used for programming needs to be capable of this.
Especially if something is 5 levels deep, it's really hard to see if you have 12 or 11 spaces (so 5 levels + 1 space or 6 levels) indentation.