But the Blood Elves don't do it. It's not there. It's a silly arguement to say, "High Elves can't have this unused look because I could imagine my Blood Elf having that look."
Blood Elves could sprout tentacles and turn purple as well... that doesn't mean Void Elves can't have their own look.
- - - Updated - - -
Sliders were around LONG before WoW came out. Even at the time of release, it had just about the most bare-bones customization possible. This was a deliberate design choice.