That's right, Bagpuss.

Say I'd taken a picture of you just after you were born -- specifically, just as you took your first breath. Would that picture "cause" or "effect" a single thing about your body, your mind, your life circumstances, or your personality?

No. It's just an (objective) picture of what you are at that moment, taken from the 'outside in'.

It's the same with the snapshot of the heavens that a natal chart provides. That snapshop displays all of your potentials and tendencies, be they recoginized or unrecognized, interpreted correctly or incorrectly, latent, or manifested, or in the process of becoming manifested - as your life circumstances and free will allow.