Because eight 7" drivers will not begin to produce the kind of LF that superior SOTA speakers can produce.
Why would you state so? Eight 7" drivers can actually displace a lot of air while still responding much faster (less mass, less inertia) than a single or dual 12" or larger cone woofers. Another benefit is the higher breakup frequency over large woofers.
I've actually heard Kii speakers in person and while having great bass, no coloration whatsoever, they lacked effortlessness, there was some kind of tension, for lack of better words and they were not the most transparent speakers I have heard.