<em>The purpose of a journaling filesystem is *only* to ease and speed the
task of recovery after an unclean shutdown.</em>
That is not quite correct. The primary purpose of journaling in typical
journaling filesystems is to preserve metadata integrity. Filesystem
repair tools cannot repair metadata that has never been written.
The secondary purpose of journaling is to loosen ordering restrictions on
meta data updates. Assuming you want your filesystem to be there after an
unclean shutdown, that is a major advantage.
Finally, journaling filesystems are not metaphysically prohibited from
using their journals to do other useful things, such as store meta-data
undo information, for example.