Well, to be fair, 'wings are considerably more open than any of the cars you mentioned. It would be more accurate to compare a 'wing to a somewhat minimalist touring roadster.
And, well, I'd have to say that the answer to why someone would choose the 2 wheeled version to the 4 is the fact that it can be more fun to take a bike instead of a car. I'll certainly agree that a 'wing is more plush than a 996, but it's still a lot closer to that than it is a Lincoln. Gets better gas mileage, too.