You can always pull into another lane to overtake like you would with a slower-moving car. The only situation I can see a cyclist making a difference like this

You can always pull into another lane to overtake like you would with a slower-moving car. The only situation I can see a cyclist making a difference like this is on an uninterrupted country road where it's dangerous to overtake. In any urban area the time lost to waiting behind a cyclist will be negligible compared to the minutes lost stuck behind cars at every red light.