It's one thing to wish that apps would put their data anywhere except dumping it in your home dir, but this is exactly why I hate the XDG spec. I want all data for a program--be it the configuration or the cache or the binary itself--to be in a single directory such that 1) "uninstalling" the program, completely and in isolation, is nothing more than just deleting that single directory, and 2) any program not doing arbitrary file I/O can entirely function while having access to only its installation directory, and nothing else on the filesystem.