Here's why:
* Two words combined: It consists of two words, "mass" and "media," that work together to form a single, unified concept.
* Specific meaning: The meaning of "mass media" is different from the individual meanings of "mass" and "media" when used separately. It refers to the broad means of communication that reach a large audience.
* Often hyphenated: While not always, "mass media" is often hyphenated, particularly when used attributively (e.g., "mass-media outlets"). This reinforces the idea of it being a single unit.
However, it's worth noting that the usage of "mass media" as a compound noun can sometimes vary depending on context and style. Some writers might use it as two separate words, especially in informal writing.