Prevent Finder from launching when quitting all applications
If you open Terminal and enter "launchctl list" it will list all of the programs kept running by launchd, the "launch daemon" that keeps system software running even after it is quit/force quit/killed/crashed.

Scroll to the top the results, and you will see "com.apple.Finder" keeping the Finder always running as long as the OS is running. Finder does much more than browse the file system, and it should always be running (same for the Dock). However, if you want to quit it and keep it from relaunching, you will need to remove it from launchctl first. I wouldn't do this personally, but here's how:


Open Terminal
Enter: sudo launchctl remove com.apple.Finder
Enter your password and hit return.


Now you should be able to quit Finder without it relaunching.

To undo this:


Open Terminal
Enter: sudo launchctl load System/Library/LaunchAgents/com.apple.Finder.plist
Enter your password and hit return.