Why, you ask? Well, it is a write-only database, which means there is no tool to actually read or fix a journal files, should they become corrupt. Or even notice the corruption. And they become corrupt all the time.
So I don’t care for the theoretical benefit of binary blob logs, as long as they don’t work at all. It’s as easy as that.
See https://bugzilla.novell.com/817778 for all the gory details.
To add insult to the injury, they are also written in a way that tends to fragment the logfiles very badly and thus the performance reading them (for the unlikely case that they are readable) is abysmal. Maybe it is usable with the latest and greatest SSD but with plain old rotating rust harddrives, it’s a PITA.