This is a small change of minor priority since you can just set the project location yourself, but per default the editor is set to clutter the home directory with project folders.
The default project location should probably be a seperate Unity Projects folder inside the Documents directory, which is commonly set through the XDG_DOCUMENTS_DIR variable. The XDG user directories are usually defined in ~/.config/user-dirs.dirs.
This is, by the way, also how the Unreal Engine 4 handles it.