Bloomberg Businessweek has a piece analyzing the trend away from the all-American (or European, or Japanese, I guess) convertible in recent years. Who knew: the allure of the convertible seems to be waning.
Many entrenched automakers are discontinuing some or all of their lines of convertibles, especially European companies like Peugeot, Renault, and Volkswagen. Convertible sales reached their peak in 2004, and have plummeted ever since, despite the introduction of a few new models (among them the convertible versions of the Mini Cooper, and Fiat 500).
It's unclear why this is happening; there are broad trends in auto sales that seem like they might be related, but it's pretty difficult to directly tie the decrease in demand for convertibles to any of them. For example: Businessweek notes that there's been a rise in SUV sales, that emerging markets like China and India have poorer air quality and thus perhaps less demand for an open-air car, and in general, young people (to whom the convertible would be attractive) are buying fewer cars.
We'd add a few more trends. For one, small cars today tend to be built for practicality and efficiency, which either take the place of or are simply elements of style (see: Fiat 500, Honda Fit, Mazda3, Chevrolet Spark). Whereas a hotshot might buy a convertible a few decades ago to show off wealth, perhaps today a hybrid reflects what that hotshot wants to see in himself or herself. Or perhaps in today's economic climate, it simply doesn't make sense to invest in a less-than-practical car with, perhaps, a less-than-stellar reliability rating (the most unreliable car in 2012, for example, was the BMW 3-Series convertible).
It's all very complicated, which is no consolation to the companies that have relied on convertible sales over the years.