They are used, but hard vs. soft realtime is tangential to the broader discussion here.
If we stick with the video game example, it has a real time goal: having frames displayed at the target framerate. The "soft" aspect comes from the fact it's tolerable for a game to fail some deadlines. It's certainly undesirable, but a few minutes of frame-y gameplay is not game-breaking.
Depending on the particular system, there will be tolerances of how frequently and in which ways a realtime deadline can be missed without constituting an overall failure of the system.
If we stick with the video game example, it has a real time goal: having frames displayed at the target framerate. The "soft" aspect comes from the fact it's tolerable for a game to fail some deadlines. It's certainly undesirable, but a few minutes of frame-y gameplay is not game-breaking.
Depending on the particular system, there will be tolerances of how frequently and in which ways a realtime deadline can be missed without constituting an overall failure of the system.