I know that the definite articles is not used with professions but there appear to be instances when the definite article is dropped, especially in the plural. I don't know if this is an informal Spanish or whether there are specific rules which indicate that a definite article is required.
For example, in English, we say : Vegetables are on sale in the market. While we would say : The vegetables are on sale to convey the meaning that the sale items are limited to vegetables.
Is the same sort of thing going on in the Spanish language?