One upon a time in Cubase clicking ‘listen’ on a channel caused the channel in question to be the loudest thing in the mix and attenuated all the others so you could easily with one click focus on any single channel.
These days it behaves the same as solo. The manual says:
The listen mode allows you to quickly check the signal that is coming from selected channels without interrupting and interfering with the actual mix. During a recording session it allows the sound engineer in the control room to attenuate the signal that is coming from one of the musicians while the recording continues undisturbed, for example.
To enable the listen mode, you need to enable the Control Room.
To enable the listen mode, click Listen for a channel.
This routes the channel to the Control Room without interrupting the signal flow.
That’s nice but why does it solo?