I am surprised to see you compare the OS X and Windows experiences. They seem completely dissimilar to me.
With Windows, it seems like every little thing needs some complex installer procedure that splats files all over the system. Every program needs dozens of DLLs, and the only way to get rid of it is to run an uninstaller that hopefully remembers everything it created, and even more hopefully doesn't break anything else on your machine.
With Mac OS X, there's generally no installation process at all. You download the app, and you put it where you want it to go, and then you run it, and that's it. Nothing goes anywhere and you don't need any special process to manage it.
The experience I've had on Ubuntu is sort of midway between these. There's a complex installation process, and everything has to deal with it, and shit gets plastered all over your machine and there's no way you can keep track of it all, but at least things generally mostly work most of the time.
But really: why manage complexity when you can do away with it?