Compression of mono material recorded in 2 (identical) channels

I just discovered that audio which is 100% mono, but is stored in a stereo file delivers a greater file size when not first converted to a single channel.

This means that there is probably improvement possible for these kind of audio files by properly detecting they are 100% mono.
Data could be compressed the same way as a single channel file, but still act as two channel (supposing there is a reason to store it in 2 channels)
And/or it could automatically (but optionally) be converted to single channel if it detects two identical channels. Optionally, because we must suppose that there might be a reason (compatibility) that a mono file is stored with two channels.

Obviously a lot of people who store their CD's in flac format for alternative playback methods will often not be aware they are actually storing 2 identical channels. For these people, enabling frontends to let the compression algorithm automatically convert them to mono can be an improvement. (about 15% less space)