Why is a great white shark's mouth bloody?

Many close-up photos of great whites are staged. People to out with a boat, and then start throwing bait into the water. Maybe even using tethered chunks they throw out and then pull back in towards the boat. Often the sharks bump or bite into the hull or the stern platform during this, which is what causes the bloody jaws.

Left to themselves, sharks would only have bloody jaws immediately after feeding. And possibly even not then, depending on the meal.