I tend to think that electronic music's reliance on visuals stems from the
lack of causal relation between the sound and how the sound is produced.
There is intense curiosity and pleasure generated by seeing how a musician
plays an instrument and what kind of sounds are obtained through such
playing. In electronic music this causality element is visually eliminated,
since sound is created in various "black box" type devices: button in, sound
out, process obscured.
Non-dance electronic music has, in my mind, suffered in live performance
because of the lack of causality. I generally fail to understand how the
experience would be in any way different, or better, than if the sound was
on a pair of good headphones. Since it is hard for the audience to know if
the laptop jockey is improvising or just pressing "play" and then pretending
to twist knobs on a mixing board, non-dance electronic music is better off
(most of the times) relying on some visuals to offset the lack of causality
on the stage (and again, remember the black box). In my mind, good visuals
provide causality to the sound; bad visuals, they are pretty wallpaper at
best. I remember seeing the band Plaid "playing" (they were completely
faking it), their visuals were really beautiful, but for the most part had
no definite relation to the sound. They were timed right, but there was no
definite cause-effect relationship. I would have loved to go to the movie
theater and seen the videos without the musicians, but being in a club
setting, I was trying to find the bar stool with the best view of the
screen.