X6 is aimed at customers who want a stylish & performance oriented SUV-like vehicle (huge dimensions = huge presence, higher sitting position = commanding position, sporty image = coupeish shape & performance capabilities vs the rivals).
Till X6 arrival such customers had to pick RR Sport, Cayenne, and top-end versions / sport packages (M, S, AMG) of X5, Q7, ML. They buy an SUV due the presence, not due the practicability. SUV as an image car - as a statement.
Now with X6 BMW are introducing something even more extravagant in an SUV sub-segment (=SAC) - a car with even greater presence & image factor. And unparalleled sporty appearence (due the coupeish shape).
Yes, even some soccer moms will opt for it - due the stylish design. The ones with max 2 children, and w/o pets etc. Modern (sub)urban moms.
The others who want more practicability will go for X5, X3, or F5 (when available; that's the car which suits perfect to modern image-conscious soccer moms / small young families with high incomes).
Mind the coupes are all about image. Is 1er coupe practical? Is 3er coupe practical? Is 6er coupe practical? NO! But people still buy them - even the less sporty models (eg. 320i, 320d, 120d, 630i, 635d), so they buy them for the image not the performance. Same case with X6.
X6 - an image (coupe) car. Yet this time it is not based on a sedan / hatch but on an SUV.
And again: wealthy people can afford to buy impractical cars (= image cars). Something we "the common people" will never understand.

And that applies not only to the cars but also to the other image-goods (clothes, accessories, jewelery, furniture etc). Image before practicability (or value-for-money factor). That the reason luxury brands & goods exist. If everyone were buying only practical & reasonably priced goods the luxury goods would not exist. Humans posses a lot of vain factor in their nature.
