Why can't I sync manually over iTunes w/o being connected to computer anymore?

I use to be able to sync my iPod Touch and iPhone 5 wirelessly without them being plugged into a power source. I could just drag and drop my files from iTunes to my device and I could sync it without having it be plugged into the computer. Why can't I do this anymore. The device is not showing up on the left hand column unless it is plugged in.I am using a Mac. Thanks!