To me, part of what makes PCs "Personal Computers" is that I don't need to go through some third party to distribute or acquire software. I don't need anyone's blessing, and I don't need to jump through hoops rooting the device or compiling from source, I just do it because it's my computer.
If all Windows applications were PortableApps, all you'd have to do when getting a new computer is copy over the directories where your applications are stored. Installs are a copy, uninstalls are a delete.