Not only do they have golden skin, but the men are starving, having already foraged other foods and hunted other animals for days. They have been trapped on the island due to winds for many days.
If Helios had notice that his cattle was gone then whoever killed his cattle would be killed by Helios. This was shown in the odessey when all of the odysseuss men dies because they ate the cattle.
Because it says so in the Odyssey.
This was a warning given to him to shun the island of Helios in order to avoid incurring the sun god's wrath. As Helios's (the sun's) gaze reaches everywhere, nothing they did would go undetected. 'Helios the sun-god, who sees all things and hears all things.' When the crew of Odysseus, who were hungry, slaughtered and ate the cattle they found on the island and so incurred the wrath of Helios, Zeus hit them with a bolt of lightning and destroyed them.
They were starving and they wanted filling foods, so they disobeyed Odysseus.
Circe warns Odysseus that the island of Thrinacia is home to the sacred cattle of the sun god Helios. She cautions him that if his men harm or eat the cattle, they will face dire consequences, including the destruction of their ship and the loss of their lives. Circe emphasizes the importance of respecting the cattle and avoiding temptation, as doing so is crucial for their survival and safe return home.
Odysseus' men get killed by Helios because they ignore his warnings not to eat his sacred cattle, which angers the god. As a result, Helios asks Zeus to punish the men by sending a storm that destroys their ship.
His men were travelling for a long time, and they were very hungry. Odysseus told them to only eat fish and other things besides the cattle. However, they were starving and went against Odysseus's' instructions, and ate the cattle.
In the end of the Odyssey, Helios threatens to stop shining his light on the gods and humans because Odysseus' crewmen killed his cattle. He demands retribution for the slaughter of his sacred cattle.
In "The Cattle of the Sun God" in Homer's "The Odyssey," the external conflict arises when Odysseus and his men land on the island of Thrinacia, home to Helios, the sun god, and they are warned not to harm his sacred cattle. Despite the warning, Odysseus's men slaughter the cattle for food, resulting in Helios demanding Zeus to punish them. As a resolution, Zeus sends a thunderbolt to destroy Odysseus's ship, killing his crew and leaving Odysseus alone to continue his journey home.
There is no need. Golden cattle are not normal. The crew already know that these are sacred cattle. They already know the consequences, so telling them that they will all die and only he, Odysseus, will survive if they eat the cattle sounds arrogant and petty.
When Odysseus left his men to go pray on the island of Thrinacia, they disregarded his warnings not to harm the sacred cattle of the sun god Helios. As a result, the gods punished them by causing their ship to be destroyed in a storm and all of his men perished except for Odysseus.
It's not that they should not touch it, it's then if they should avoid touching any of his belongings, in which when Odysseus falls asleep. Eurylochus & the crew were starving in which they Slayed Helios' Cattle and Ate them. So, Helios, in a rage, went to Zeus and asked him to punish the men for stealing from him and eating the "Cattle of the Sun" in which Zeus sends down a lightning bolt destroying Odysseus' ship as well as killing everyone including Eurylochus except for him, Odysseus.