There’s also heal-toe shifting. If done correctly, it puts less wear on your transmissions (syncros, in particular), and is also smoother. It’s a quick blip of throttle while downshifting under braking.

So it’s not just a racing technique, though it is debatable how much it matters. Modern transmissions are pretty reliable as long as you don’t abuse them. Rest of the car could easily disintegrate around it before the syncros get ground away.