Why doesn /bin/sh point to bash?
Solaris uses the Bourne shell (/bin/sh) as the default system shell to satisfy backward compatibility with historic releases of Solaris. (Many of the included system scripts have been written to use /bin/sh, so backwards compatibility is an absolute must.) There is work being planned to replace the Bourne shell with a generic POSIX compliant shell. Whether that is an updated bash running in POSIX compatibility mode, or another shell such as ksh93 is still an open question. Either option require additional coding resources to implement. Indiana has made /bin/sh point to ksh93 in the 2008.05 release.