wsrep.cnf is not loaded

cat /usr/local/etc/my.cnf

<snip all but the last line>
!include /usr/local/etc/wsrep.cnf

# ls -la /usr/local/etc/wsrep.cnf
-rw-r--r--  1 root  wheel  3592 Aug 12 22:54 /usr/local/etc/wsrep.cnf

So why doesn't it load wsrep.cnf??