Here's why:
* Adverbs modify verbs, adjectives, and other adverbs. They describe how, when, where, or to what extent something happens.
* Nouns name people, places, things, or ideas.
While some nouns can be used as adverbs (often with the addition of "-ly"), many cannot. For example, you can't say "He walked chair" or "She sang happiness".
Here are some examples of how nouns can be used as adverbs:
* Time: "I'll see you tomorrow."
* Manner: "He spoke softly."
* Place: "They live downstairs."
* Degree: "She was completely exhausted."
However, these are usually formed using specific suffixes or structures:
* "-ly": "happily", "quickly"
* "-wise": "clockwise", "otherwise"
* "ways": "sideways", "anyways"
Many nouns cannot be used as adverbs directly and would need further modification to express an adverbial meaning.