Why can't the men eat any of the fine herd of Hellios cattle that they find

Before landing on the island, Odyyseus has been told not to touch the Hellios cattle because they belong to the sun. When the men run out of provisions, they slaughter the cattle while Odysseus is away. The gods kill all of the sailors in anger, and Odysseus is the only one allowed to live, as he had no part in their actions.