You're right that many demos simply exist to showcase technical brilliance, but many in the demoscene are starting to trend further towards expressing artistic ability. Some examples off the top of my head:

- Number One/Another One by CNCD/FLT: http://www.pouet.net/prod.php?which=77399

- When Silence Dims the Stars Above by Conspiracy: http://www.pouet.net/prod.php?which=75713

- Aurora by Excess: http://www.pouet.net/prod.php?which=75791

- Along for the Ride by Ümlaüt Design: http://www.pouet.net/prod.php?which=78053