Freshmaker
I am Korean.
It's understandable because when it was written and produced, IIRC, they hadn't yet shown in the manga or anime that Super Saiyan was an "unlockable" thing as opposed to something that could only come out when you're angry.
I think the only real reason they did it was because SS was so powerful that the fight (and the movie) would be instantly over once Goku went blond.