The profit margin on a cruiser is higher than any other type of bike, and there certainly is room for growth as far as market share goes, so they stay in the US cruiser market. Industry wide, cruisers accounted for 50% of the bikes sold in the US last year, will all other types put together making up the other 50%. As the riding public ages, sportbike sales (where Suzuki sells most of their bikes) are expected to continue to shrink while cruiser and tourer sales continue to grow, so Suzuki needs cruisers in the showroom.
But looking at that data makes it easy to understand why Suzuki only adds one new cruiser model every couple of years, keeps those models in the showroom for 10-20 years before replacing them, and why they sold the re-badged Kawasaki Mean Streak: when you only sell 15,000 cruisers a year, you really need to limit your development costs and sell a bike for a lot of years to recoup those costs.
Suzuki's car sales have grown considerably in North America, but the dealer network is still a bit thin, and Suzuki's production capacity for US-legal models is limited. But again, they sell a lot more cars in Asia than in North America, so expanding US and Canadian sales in not on the top of their priority list. China is currently the second-largest auto market, and also the fastest growing, so that is where Suzuki is pushing thier cars the most.
Personally, I think Suzuki would be a good match for a merger with Daimler-Chrysler, with Suzuki providing low end cars, Benz the high-end cars and commercial trucks, and Chrysler/ Dodge everything in between. But that's just me.