One obvious reason: because a journaling filesystem on a camera very likely would not have helped you (or anyone).
As a very high level overview, here's what a journaling filesystem does: Before each write to the metadata (or data, if data-journaled as well), first write what you're going to change to the journal. Only once you're sure that's on disk, go ahead and write the change. Basically, this means that if power is interrupted during the write, you can recover the filesystem by using the journal—you go ahead and perform any actions in the journal.
This is valuable on a desktop PC, where the power might go out, or the user may hit the reset button, or pull the plug, etc. Also valuable, but less so, on servers (power failure) and laptops (reset button).
A camera is battery-powered. It has an off switch, but this normally tells the firmware to shut it down—it isn't a physical power disconnect. There isn't usually a reset button, or if there is, its basically never used. So, you don't need journaling, the firmware can just finish the write. The only exception would be if you physically removed the battery. Maybe that'd happen with an external power pack, but other than that, a camera should never experience an unclean shutdown.
Also, almost no flash devices actually handle unexpected power failure well. Get them in the middle of a sector relocation (wear leveling), and all bets are off. So even if you had a journaling filesystem, you'd still not be safe from power failure.
A journaling filesystem does not protect you from:
- Bugs in the flash controller on the SD, etc. card.
- Bugs in the camera's SD host hardware
- Bugs in the filesystem code on the camera
- Bugs in the firmware's SD drivers
- Loss of sectors on the media
- Hardware malfunction (e.g., due to cosmic rays, static discharge, EM noise, water, ...)
In fact, a journaling filesystem is more complicated, so you are actually more likely to have filesystem bugs. It amplifies writes, so you're more likely to hit flash controller or SD host bugs. And you're going to wear out the flash slightly sooner.