The vast majority of the kit lenses sold with entry-level (or even upper entry-level) interchangeable lens cameras, tend to have an aperture range of f/3.5-5.6. This seems to be independent of whether you look at SLR or mirrorless cameras, which manufacturer you look at (Canon, Fujifilm, Nikon, Olympus, Panasonic, Samsung and Sony all make a f/3.5-5.6 kit lens) and also of sensor size (you can find a f/3.5-5.6 kit lens for all of Nikon 1, micro 4/3s and APS-C). About the only counter-examples I can find are the Pentax Q7 and Fujifilm X-E1, both of which have an f/2.8-4.5 lens. However, the Q7 with its relatively tiny sensor isn't exactly typical, and the X-E1 is definitely aimed a bit higher in the market - the cheaper X-M1 ships with a f/3.5-5.6 kit lens.
Is there anything "special" about the f/3.5-5.6 range which means that de facto every kit lens has the same aperture, or is it just a combination of engineering realities and no manufacturer being prepared to take a chance on "something different"?