The Mid 2011 Mac mini was one of the first Macs to have Thunderbolt connectivity ( full list of Thunderbolt-equipped Macs). There’s virtually no demand on the Mac mini front, so it’s not often you see an eGPU setup with it.
There is definitely demand for a more powerful GPU setup from Mac Pro users.
But what about Mac desktops that have no standard PCIe slots? The Mac Pro trashcan and Mac mini are such machines.
External GPU implementations have proved to be successful for Mac laptops.