I don't consider any sort of unpacking to be a big deal. The only thing that takes more than a few seconds to get out of the box is the case, and that's only if you got a really big one (full tower, etc).
As for the difficulty in removing things such as a motherboard, it all depends on your case and other extraneous things such as your cooler. Generally, I also don't like the fact that I'm without a desktop PC while doing it.
Plus, you're forgetting the biggest benefit of all.... Getting all of those PC parts makes it (what I call) a "Geek's Christmas". Instead of wrapping paper, we get NewEgg boxes. :awe:
This. If assembling a new rig is something that brings anything less than excitement then you are probably exhibiting signs of not wanting to be a DIYer for reasons xyz (real-life time constraints, simple lack of interest, etc). Plenty of businesses cater to that portion of the enthusiast segment, ain't no shame in it. You can still love your box even if you didn't love building it. (hmmm...that just sounds wrong)