I can't speak for the staff but I've used the method of .dat file bundles in one of my own scripts and to update the distribution you have to rebuild the tar file as well as update change logs etc and so the download area only gets updated at certain intervals otherwise it would take a lot of work to constantly update after each fix.

Hopefully most people view the bug fixes forum and so they can use the patch until the next download is available.

Alex or Jason will obviously give their actual reasons, I'm just speaking from my own experience.