I'm curious why some apps write entire folders in the Applications folder, while others just result in a single file. So far, it would seem that most apps that use an installer result in a single file, whereas apps that need to be unzipped result in a folder that you copy in its entirety in the Applications folder
Open a Terminal window and go to /Applications. Then do a:
Surprise! All applications are in fact "directories/folders". It's only the Finder gui that shows you most of them in the form of a file.app instead of the folder for simplicity (probably).
(I believe it will depend on the metadata for the folder. Someone could correct me if I'm wrong)
You can still access the folder/application contents from Finder if you right click and choose "Show Package Contents".