I'm not sure what it is about sound design that I love so much. Perhaps it's growing up around Ben Burtt Sr. and being aware of sound in movies from such an early age. Or, maybe it's hearing all the stories from Ben Burtt Jr. about the amazing adventures he gets to go on to record sound effects.
However, I think it's something more than that. I think that sound in movies is still magical (how apropos!) Trickery in sound is like a good optical illusion. Ben rubbing balloons together to create the sounds of rocks ripping apart and scrapping against each other in the climax of Indiana Jones and the Last Crusade is mind bending once you know about it. Those scenes sound and feel so real that when you find out how the sound was done, it's completely astounding.
The other side of the coin is that these days, sound can be the most real thing in a lot of these movies. Sound grounds fantasy in reality because it plays in the subconscious. If you believe the soundscape then the images become that much more real - and consequently, the story. That's a given, even back in the hay day of practical special effects. Now though, it's easy to write off the special effects work as CGI and leave it at that. But sound is still, by and large, real. In a Michael Bay movie, the explosions might be CG, but the sound effects are of real explosions. The muzzle blasts of gun fire might be CG but the gun shot and ricochet sounds are real. Even when one sound (a radiator) is being used in the place of something different, (a starship) they are real sounds. Sound might be affected with computers. It might be augmented and tweaked, but few sounds are actually created in the computer from the ground up - and that makes all the difference.
Just look at these scenes from Harry Potter. Watching the sound designers actually knock down piles of furniture and set real things on real fire is really exciting to watch - and you can feel it when watching the movie. For something so fantastical to feel so grounded is a feat. Sure, the writing of Rowling and the attachment to the characters and the emotions is a huge part of it - but in cinema you need the orchestration of the technical artistry and the story artistry to come together if you want one or the other to work.
Something else this little documentary shows off is that this attitude clearly went further than just the sound. Real sets were built for all the scenes shown. Sure green screen was used to create set extensions, but by and large, the reality that they tried to create through all these techniques really pays off.
If you have bothered to read this whole post, then you might want to check out more of these documentaries about sound at soundworks. It's a great series.