When I ski, I turn a lot. Bumps require lots of ski movement. Avoiding trees in powder or making eights from my wife's short radius turns require lots of ski movement and acceleration. Dodging the masses on the Mountain run groomer (human slalom) requires lots of ski movement. Tricks throw the skis around a lot (my day isn't right until I throw a helicopter). Saving an off balance situation requires quick ski movement. Everything else is just getting to the fun stuff. My skis move a lot!
The developing skiers I drag around the mountain need to follow my whippety turns. When they make a mistake, a quick and significant correction is needed - or they fall. And the fall aftermath is much easier with a light ski.
Jaws surfboards, straightline skis and wrecking balls, while they move fast, do not move dynamically and their weight is not a disadvantage. Anything that turns or accelerates gets an advantage from being light.
I'm old. My skills aren't perfect (but I am the best skier on the mountain!). I'd rather turn than just ski blistering fast. Eights are cooler to me than elevens. Bumps rock. Groomers suck - even more if they flatten the bumps. Tenths of a second aren't worthy of stressing over. Keeping skiing as I age is important. Light equipment helps all my goals.
As an engineer, light does not equal flimsy. As an athlete, taking advantage of quality equipment is not a fault. I'm bummed by all the love of the ski tanks I see. Magazine covers don't show turning. Intermediates would rather go fast than turn (to avoid crashing into me). And heavy equipment does stress my body.
Turns rock! Light skis rock!