There may be legal reasons for not deleting an account. I know I wanted to delete a former employee's account from a site, but it was declined. All I could do was to change his PW to something he didn't know. But that was a government related site.
For an employee or former employee, it would NOT be done just in case you ever needed to go back and do some digging. For a website, I'd love to hear a "legal" reason why it can't be done as I'm certain there isn't.
Makes you think the OP wants to cover any tracks of theirs... Good luck getting Google to remove the data they've collected though !