Ignoring or throwing out those “wrong” last names can be a mistake. I have the maiden name of my ancestor born in 1851. I’ve clearly identified her father through a variety of records (vital records, estate records, and property records), but originally I thought she had a different last name–the last name of her step-father.
Do I still need that name?
Yes. Not because that last name was her last name at birth, but because at any time after her mother’s marriage to her step-father in 1859 and her marriage in 1869 this ancestor may have been listed with his last name. She still may appear under her maiden name in the occasional record after 1869 as well.
Wrong names can serve genealogical purposes. They can be clues as to non-biological relationships our ancestor had with other people and can be names under which they are listed more than once. Don’t forget about those wrong names once you have determined they are wrong. They could still be a clue.