Huh? Extra weight? Have you even held a surface? Clearly you don’t understand.
Of course I've held a Surface. . . and I understand better than obviously do you. ANYTIME an engineer adds mechanisms to a device, such as the kickstand, it adds extra weight over the option of not adding mechanisms. . . or he must trade off not adding something else, for example extra batteries for longer use. . . or perhaps a cellular radio and antenna because of the space occupied by the something he's added. Choosing a kickstand over a cellular radio or extra batteries was an engineering or a marketing choice.
Which one do you think it was? Looking at the ads showing ecstatic dancers clicking and kick standing, I think it must have been marketing. . .