Film has a couple tricks to add weight to a moment. Say someone gets shot, or there's an explosion. You film it and play it back and there's not much oomf there. So the movies film the same explosion or car crash from several angles and play it back to us 1-2-3. We're so used to this cinematic trick we don't usually even notice, we somehow see it as one explosion. But that's not all that easy to do in a videogame. Possible, sure, but not easy. Not as easy as IRL anyhow. So we use movies other trick: slow motion.
Slow motion in film doesn't just help add weight to a moment, though. Came across a thing recently in Johnstone's Impro where he pointed out that making the hero move in slow motion confers status to them. There are many things we're wired to imagine as high-status, and one is people moving slowly. A minion or lackey may hurry to get out of the way or fidget with anxiety, but a king will take their own sweet time. Thus the slow-motion scenes in movies.
There are still other reasons I love time dilation. (I won't call it 'bullet time' since the term has been trademarked or copyrighted or something.) One of which is it can turn a twitch game that my forty-something-year-old reflexes are hopeless at into a strategy game - it makes Viewtiful Joe and Spider-Man and sixty second shooter accessible to me.
But even if you don't have a specific time dilation power-up or mode or button in your game it's still useful to have time dilation built into your engine. Consider the 'freeze frame' you often see in a fighting game after a good hit - it adds additional feedback and weight to the moment. A 'freeze frame' is usually implemented as time slowling down a lot for a very short period of time - because if time actually stopped you might get some divide-by-zero errors with your delta t. For a fight game in particular, this is something the designer is totally within their rights to expect the programmer to provide. (Because it should take them, like, two minutes ... though it might take a lot longer to then provide the hooks for the designer to get at it.) And even without a freeze-frame, adding that weight-to-the-moment for the awesome combo or the kick-ass weapon or stealth takedown can be done with good old slow motion.