As someone said earlier, if someone buys something, it's their right to do to it what they want.
For a regularly gigging rock/metal musician, I know that people turn up to gigs to see the show, if they wanted to just listen to the music, they'd put on a CD. If you're terrified of damaging your instrument then you end up stood still or trying to avoid the guitarist who's giving the audience the show they came to see.
One of the CLASSIC guitar moments is Hendrix lighting a candle on his guitar, that's hardly respecting his instrument but it's something that I'm sure everyone knows about because it's not just a guitarist stood about playing.
In saying that, I believe any instrument should be looked after. It's ok having a pristine guitar but if none of the electrics work consistently, what's the point? I've seen FAR more guitars that barely look used but barely work than guitars that're battered about but never cut out and still have their original tone.
None of my instruments are very battered (a few scratches, a ding where it fell on the edge of a cymbal etc) but without close inspection they all look near enough perfect. It's purely chance though, they've been battered about, they're just holding up incredibly well. But none of them cut out or have lost any tone which is way more important to me.
And this ties in with the tools thing too, you don't keep your tools perfect because you want them to look nice, you keep them perfect because you want them to work perfectly.
Edit: I ought to add that of course it's up to the owner and of course different music requires different stage shows. Just because you're not diving about, it doesn't mean you're not putting on a show.