Why can't Firefox do what Skype and Miro do (below)?
* If the user string contains Windows, provide an MSI. In these OSes, if you click on a MSI package, it installs.
* If the user string contains OS X, provide a install image. In these OSes, if you click on an install image, it installs.
* If the user string contains Debian or Ubuntu, provide a dpkg. In these OSes, if you click on an dpkg, it installs.
* If the user string contains Fedora, RHEL or SuSE, provide a rpm. In these OSes, if you click on a rpm package, it installs.
* Anything else gets a menu with all the above options.
How about they wait until available through their distribution's package manager?
Most people don't wait 6 months. They use articles like the one mentioned, and are more likely to encounter poor-quality Firefox as a result.
Additionally, distros tend to want to manage the package building themselves. Some groups want to add in tweaks or configuration templates. Others want to include their own pages or optimizations. We can't logistically consider trying to manage all that centrally, nor would we want to take the control away from those distros.
So, I agree, you do get a slightly less comfortable distribution mechanism for the browser. You get additional control and choice depending on the distro you chose though.
What Mozilla does endeavor to do is make sure that the core code works well on all three platforms. That is where we feel it is most valuable to dedicate our resources.