I think Google are trying to emulate Apple in the sense of creating a new market. Tablets existed before the iPad but it was the iPad that made them cool and desirable. At the time I couldn't see the point - you've got smartphones and netbooks for mobile use and laptops and desktops for the rest - but I was wrong. There was a whole group of people out there who use a PC mainly to consume but wanted something simpler.
I think Google want the Chromebook to be similar, somewhere between a traditional laptop and a tablet - more than a purely consumption device but simpler than a trad laptop. And by making a shiny shiny (and pricey pricey) version they are attempting to make it cool.
Again it's not for everyone but it doesn't have to be.