If the honesty of a user is questioned after taking copies of the company’s intellectual property and you have the ability to authenticate as that user, would you really want to be caught up in that legal maelstrom? No thanks. Another reason why I have no knowledge of other people's passwords.
Company I work for you can be dismissed for asking a user for their password. If you need to access there machine then we are to reset the password and use that password. Then when we are finished force the user to reset it again.
I guess this saves a issue people using the same password everywhere and it getting exposed.