I would guess that the xi models in the 3 series don't sell enough to warrant expanding into other lines. Especially since they've introduced the x3 and x5. But as many on this board and other boards will reassure you - AWD isn't the end all and be all of driving in bad weather. BMW DSC keeps you on the road nicely in snow, rain, and ice so long as you're not driving out of your own element.
Seriously though - if you want actual demonstrations - goto the BMW performance center and take one of the courses (I think they're $399) and see how they handle on wet and greased pavement in emergency situations.
As for the coups not having it... I'd say that a lot of people argue that RWD makes a car more fun to drive. And if you're buying a coup that may be what you're focusing on. The xi option also changes the suspension and ride height.
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