|Salmon scales. Canon S120|
There are many parts of food which are 'optional'; some like to eat the skins of jacket potatoes for instance, while others leave the skin of fish.
One issue that can occur with fish skin is that the scaly fish versions are often a bit of a lottery to prepare and there is a chance one of the chewy plastic bits may remain.
There are some cultures that see the chewy parts as the best bits however!