To start, the base model Kizashi came with 16 inch wheels from model year 2010 to 2012. Which trim and model year you have determines whether you have factory 16, 17, or 18 inch wheels.
Also, a lot of talk about 16 inch wheels for winter tires comes from people who have a totally separate set of winter wheels and tires. Basically, they purchased additional wheels and tires not original to their specific Kizashi so they can swap out their Summer wheels and tires quickly and easily for their Winter set. Because they needed to get wheels in addition to winter tires for this, they got wheels of their own choosing. Many people get 16 inch wheels for the winter because they are not only cheaper, the smaller size makes for better snow traction. A 16 inch tire of the same type will handle better on snow than a bigger and wider 18 inch tire. This is because the narrower tire can sink in a bit more to grip snow rather than roll on top. It's a bit counterintuitive and opposite from dry traction but just a reality of snow traction.
So again, the Kizashi came with different sizes based on trim and model year but for a winter set, it makes sense for many to get 16 inch wheels and tires.
2011 Suzuki Kizashi Sport GTS 6MT (Black)