[derefr]

There are some little things a Mac Mini has that you can't get by just (essentially) Hackintoshing a NUC.

For example, Apple's custom UEFI, plus a Bluetooth controller that boots in HID mode and loads configured pairings from NVRAM, allows you to "hold down [key combination] at boot" on your Mac Mini's Bluetooth keyboard.

Or the fact that all the desktop Mac models have internal speakers (and not just the motherboard PC speaker kind) and internal microphones, so OSX can guarantee it always has those devices available to use to play system event notification sounds, or for Siri, or for FaceTime, or for visual-impairment accessibility tooling, etc.

Or the fact that you can still plug FireWire or DisplayPort devices into a Mac Mini through its Thunderbolt port (with a passive adapter to map the pins) and the motherboard will happily accept the device; whereas no PC would have any idea what to do with those wire protocols, even if you plugged them into the port of an explicit Thunderbolt PCIe card you bought.

If you could get these things from a NUC, then sure, there'd be no point in the Mac Mini.