You don't?
No. Remember I said visual appeal. The Mac Pro certainly has cleaner lines and you don't see the DVD drive lines and such, but that's about the only difference.
I actually find the few thousand holes in the front of the Mac Pro to be quite ugly and I always have. And it's just way too much aluminum/silver color. I personally liked the old QuickSilver and B&W G3 myself. Also, you may want to take a look inside of the rest of the lineup before claiming it is inside of all of Apple's hardware, especially the Mini. It's nowhere near clean with the antenna wires and such on top. Granted, it's a piece of engineering, but it's not aesthetically pleasing.
Besides, when I had a tower, I never looked inside unless working on it. I don't think anyone really cares but geeks.