Generally being succinct goes hand and hand with being zero knowledge. The proof must be MUCH smaller than the whole computation or even the inputs (otherwise,

Generally being succinct goes hand and hand with being zero knowledge. The proof must be MUCH smaller than the whole computation or even the inputs (otherwise, just provide the uncompressed image!). And the proof has to resist forgery. So going for succinctness and at least computational soundness gets you to zero knowledge 'for free'. Plus as the dead sibling comment notes: You may want disclosed modifications like a crop or redaction where the committed information remains private but you want to keep the proof.