Earlier quoted context omitted.
Simplicity? My grandma doesn't want to buy an "external display", she would truly have no idea where to even start to do that. And then after she's got the Mac mini, the external display, and the cable to connect the display (assuming she was able to find the right one,) someone then has to set it up for her. Compare that to an iMac. Go to the Apple store, drop $1k, take it home, plug in the power cable, and she's on…
That's quite a price premium to pay for 5 minutes extra work!
Very pleased, saved ~$200 off list. Still get a warranty.