Why does rpmbuild generate a dependency on /sbin/sh when I build my package?

Issue

• Why does rpmbuild generate a dependency on /sbin/sh when I build my package?
• Output at the end of the rpmbuild process:

Processing files: e-jboss-as-4.3-1
Requires(interp): /bin/sh
Requires(rpmlib): rpmlib(CompressedFileNames) <= 3.0.4-1 rpmlib(PayloadFilesHavePrefix) <= 4.0-1
Requires(postun): /bin/sh
Requires: /bin/sh /sbin/sh
Checking for unpackaged file(s): /usr/lib/rpm/check-files /var/tmp/e-jboss-as-root
Wrote: /usr/src/redhat/SRPMS/e-jboss-as-4.3-1.src.rpm
Wrote: /usr/src/redhat/RPMS/x86_64/e-jboss-as-4.3-1.x86_64.rpm