stream/list only returns live streams. A “stream” is by definition live. “Channels” would include both online and offline channels.
Also, if you are intending your application to only support Twitch channels, I’d recommend using the Twitch Kraken API instead of the legacy Justin.tv API.
https://github.com/justintv/Twitch-API/blob/master/v2_resources/streams.md#get-streams