Why would someone need waterproof luggage?

I was poking around online looking for luggage for my “fantasy vacation’.  I came upon a site that listed a lot of different brands.  Two of which I’ve purchased before.  And then I noticed the Rimowa brand.  Very nice stuff!  Very pretty too!  I thought that the price was maybe for like a whole set, but it wasn’t, it was for one piece!  $500-$600 for one piece of luggage!  I’m not sure why someone would need splash/waterproof luggage.  I’m thinking if your plane goes down in the water, you wouldn’t need your luggage anymore.