While Daniel Foré adequately explains the design decision, it does not answer the actual question. You can get the old desktop paradigm back by installing the Nautilus file manager (part of the GnomeGNOME project). Also Nautilus will appear inside Slingshot as a second, alternative filemangerfile manger to Pantheon FilesFiles.
Install Nautilus without all the related GnomeGNOME packages and dconf-editor, by running the following command in terminal:
sudo apt-get install --no-install-recommends nautilus dconf-tools
Edit the following config entries by running
dconf-editor
in terminal or starting dconf-editor from Slingshot:org.gnome.nautilus.desktop
Check entries you'd like to see on the desktop
org.pantheon.desktop.cerbere
Add
nautilus -n
so the entry should look somewhat like this:['wingpanel', 'plank', 'slingshot-launcher --silent', 'nautilus -n']
Run
nautilus -n
org.gnome.desktop.background
Tick the show-desktop-icons box
Based on the blog post "Enable desktop icons and right click on Elementary Freya OS."