Selected answers from the Dumb SEO Questions Facebook & G+ community.
Richard Hearne: To see how it renders on desktop. Google doesn`t want to serve bad user experiences to either desktop or mobile users. Until we`re 100% mobile usage, you can expect to be getting requests from desktop user agent.
Richard Hearne: As long as there is a large proportion of desktop users, you`ll likely see Googlebot crawling as desktop. Quite normal. Also required due to dynamic varying of response based on user-agent.