There's only a slight satisfaction that comes from snapping your smartphone into its case. As designers we know that the case was injection-molded specifically for that phone, with a 0.005" tolerance and some draft angle; in other words, the damn thing is supposed to fit perfectly. Similarly, a diner will enjoy the concept of a turducken more than the chef who put in the elbow grease to cram all of those meats in there.
However, there's a huge amount of satisfaction that comes from slipping one object inside of a second, unrelated object and finding out they fit together perfectly by pure accident. It pushes our OCD buttons and our brain's pleasure centers light up on the MRI. I have no idea why this is, only that it is, and now there's a Tumblr I can't stop looking at called Things Fitting Perfectly Into Other Things.
At press time there were some 27 pages of submissions, so this oughta keep you busy for a while.