They're just showing off! Stop showing off, Arenanet. No one likes a show off, ESPECIALLY when they're pretty. As if the PvE action stuff wasn't showy enough, the flyovers of intricately produced cities and other superlative-stretching environmental features are just too much. And then that dude totally decks a centaur... and what is that robot thing?!
Really, everyone's impressed, you can go be humble in the corner now. Christ.