Here's why:
* Pronouns stand in for nouns. "Anything" refers to a nonspecific thing or things.
* Verbs express actions or states of being.
Example:
* Pronoun: "Did you see anything interesting at the museum?" (Anything replaces a noun like "object", "artifact", or "artwork")
* Verb: "I saw a beautiful painting at the museum." ("Saw" is the verb describing the action of seeing)