[chongli]

Think of a circular library with a central atrium and bookshelves arranged in circles radiating out from the atrium. In the middle of the atrium you have your circular desk. You can put books on your desk to save yourself the trouble of having to go get them off the shelves. You can also move books to shelves that are closer to the atrium so they're quicker to get than the ones farther away.

So what's the problem? Well, your desk is the fastest place you can get books from but you clearly can't make your desk the size of the entire library, as that would defeat the purpose. You also can't move all of the books to the innermost ring of shelves, since they won't fit. The closer you are to the central atrium, the smaller the bookshelves. Conversely, the farther away, the larger the bookshelves.

Circuits don't follow this ideal model of concentric rings, but I think it's a nice rough approximation for what's happening here. It's a problem of geometry, not a problem of physics, and so the limitation is even more fundamental than the laws of physics. You could improve things by going to 3 dimensions, but then you would have to think about how to navigate a spherical library, and so the analogy gets stretched a bit.