Are you certain that this is just laziness on ASUS's part, or does ASUS only post updated 3rd party drivers on their web site after certifying that they work with ASUS products?
For example, if Intel fixes a bug in one of their chipset drivers and posts the updated driver on their web site, do I know that the driver has been tested yet on my particular ASUS motherboard?
I'm always reluctant to just "grab the latest driver" without knowing that the driver has at least been tested with my motherboard.
I'm not defending ASUS or any other motherboard manufacturer here. It's certainly possible that ASUS is simply lazy in not posting the newest 3rd party drivers on their web site. But I'd like to believe that ASUS and other reputable motherboard companies have a testing/certification process that tests 3rd party drivers to ensure they work correctly with their motherboards before making those drivers available on their web site.
Of course, we consumer are free to pick up our drivers wherever we can find them, including the manufacturer's own web site. I'm probably a bit more cautious when it comes to installing 'low-level' drivers (like the BIOS and the chipset drivers) because of the potential for breaking my system in strange and mysterious ways.