My MacPro is the hub of our home. Yes, we all use MacBooks, iPads, iPhones and Apple TVs. But the MacPro is where our libraries are. All of our iDevices sync with the MacPro. All of our Apple TVs pull their photos from this device (We use the flat screen televisions as digital photo frames when the TVs aren't on.).
There are times that I use it when I need multiple monitors. I believe the desktop computer still has its uses. I do admit that weeks sometimes go by with no one touching it.