Examples of the latter include audio and video playback and video games. Nobody wants pauses or glitches, but if you get one once in a while, nobody dies. So people deliver these on non-RT operating systems for cost reasons.
No. This is a common misconception. The distinction between a hard realtime system and a soft realtime system is simply whether missing a timing deadline leads to a) failure of the system or b) degradation of the system (but the system continues to operate). Safety is not part of it.
Interacting with the real physical world often imposes “hard realtime” constraints (think signal processing). Whether this has safety implications simply depends on the application.
On the one hand they aren't safety critical.
On the other, I can imagine someone getting chewed out or even fired for a pause or a glitch in a professional performance.
Probably the same with live commercial video compositing.
But there are plenty of performers who apparently rely on Linux boxes and gumption.
Do you really stand by the statement of this rhetorical question? Because if yes: this attitude is a big reason for why web apps are so unpleasant to work with compared to locally running applications. Depending on the application, even 16ms vs 32ms can make a big difference.