Why show concept cars?

I'm hoping some of the vergeoisie will be able to explain to me why companies like Samsung would bother showing up with a TV that's 5 years off or more. It seems like they're exposing all of their work to competitors. Apple's been very successful by surprising everyone, regardless of how long they've been working on a product, and I know Apple isn't the only successful models, but it still does seem counter-intuitive.

The only thing I can think of is that they want to impress investors, but it still doesn't seem like enough, they will be impressed and the stock will either goes up slightly now or goes up significantly in 5 years.

So, what's up? Why all the concept cars from these big companies?