What's the purpose of a dark form?

I guess I’m the oddball here. I prefer a more cute aesthetic. Think Mavis. Zing! Anyway, I think once a sims is turned, the game should react different depending on age. For example, child and teens will only have a normal form. Once they age up to young adult, cas opens so they can create a dark form, or opt out. If already a young adult or over have cas do that when turned. They could even make them aspiration rewards. Fulfilling the good vampire one might reward you with the opportunity to purge your dark form. They could do one for the opposite, bad vampire, removing your human form, becoming eternally demonic.