Here's why:
* Common nouns refer to general, non-specific things. They are not capitalized unless they begin a sentence.
* "Residence" refers to a place where someone lives, but it doesn't specify a particular place. It could be a house, apartment, condo, etc.
Examples:
* "My residence is in the suburbs." (This is a general statement, not referring to a specific place.)
* "The White House is the residence of the President of the United States." (Here, "residence" is used to refer to a specific place, but the word itself is still a common noun.)
Compare this to a proper noun:
* "I live in New York City." ("New York City" is a specific place and is capitalized as a proper noun.)