The non-DRMed steam game will stop working after a while if you haven't logged into steam after a very long time. If steam ever went under, your locally installed single player games that work offline will stop working. Ask me how I know.
I've taken to getting a cracked copy of every steam game in my library so that steam can't screw me over again in the future.
I've taken to getting a cracked copy of every steam game in my library so that steam can't screw me over again in the future.