Here's why:
* Street names are proper nouns, but they are not titles. Titles of books, movies, songs, etc., are enclosed in quotation marks.
* Street names are usually part of a larger address. You wouldn't put quotation marks around the city or state in an address either.
Example:
* Correct: 123 Main Street, Anytown, CA
* Incorrect: 123 "Main Street", Anytown, CA
However, there are some exceptions:
* If you're referring to a street name that is also a common phrase: For example, "The "Street of Dreams" neighborhood is very popular."
* If you're quoting a direct speech that includes a street name: For example, "He said, 'I live on Elm Street.'"
In most cases, you can safely leave the quotation marks out when writing street names.