[Perfectlap]

"The departure of the 200 also shortens the list of open-air cars available for less than $30,000. There's the Mazda MX-5 Miata, the VW Beetle, the Fiat 500c, the Mini Cooper, the Smart ForTwo Cabrio and the Mustang — and nothing else."


That's your problem right there. Millenialls have no money so $30K and up prices them out.
Babyboomers at Medicaid age aren't free spending on anything as they're expected to live longer and need to stretch out those dollars longer.
So it's basically the Gen X'ers and a segment of the baby boomers how have the means. They're more in love with bloated sedans and SUV's in the big ticket categories. The image of being wealthy and exclusive means Range Rover or E class/Audi/Bimmer etc. and not the California tanning machine cruiser.
So what's left? Those interested in a convertible but not wanting to spend more than $30k.
Two chick cars (beetle, Fiat) a muscle car (Mustang) and the now old hat Miata(to the average non-enthusiast) are simply not enough options to support an increase in convertible sales. More like a steep drop.