  To answer Wheeler's question "Why the quantum?" via quantum information
theory according to Bub, one must explain both why the world is quantum rather
than classical and why the world is quantum rather than superquantum, i.e.,
"Why the Tsirelson bound?" We show that the quantum correlations and quantum
states corresponding to the Bell basis states, which uniquely produce the
Tsirelson bound for the Clauser-Horne-Shimony-Holt quantity, can be derived
from conservation per no preferred reference frame (NPRF). A reference frame in
this context is defined by a measurement configuration, just as with the light
postulate of special relativity. We therefore argue that the Tsirelson bound is
ultimately based on NPRF just as the postulates of special relativity. This
constraint-based/principle answer to Bub's question addresses Fuchs'
desideratum that we "take the structure of quantum theory and change it from
this very overt mathematical speak ... into something like [special
relativity]." Thus, the answer to Bub's question per Fuchs' desideratum is,
"the Tsirelson bound obtains due to conservation per NPRF."
