I think there are a lot of factors at play here.
One is that virtually every other company not only has to compete with Apple, but with each other. So they have to cram the most features and specs they can into a product, while making as cheap as they possibly can, in order to stay competitive.
For example, take a MacBook Pro, and find ways to make it cheaper: Well, we can replace the unibody aluminum with a plastic shell. We could remove the backlit keyboard. We could replace the glass touchpad with a cheaper part. Take out the Firewire port. Hey, look what's left: a cheap laptop. Everyone tries to get it cheaper and cheaper so they can outsell the other guys. Meanwhile, Apple puts in whatever they want and charges whatever they want, because they've built themselves up a position where they know people will still go ahead and pay it.
Also, because of the tight competition, companies are afraid to take risks. Remember when the USB por had just been introduced? This was a real chicken and egg situation for PC makers. No PC maker wants to be the first to switch to all USB ports because (a) it will cost more money to put the new ports into the board, and (b) they know it will annoy customers who will have to buy all peripherals. Customers will simply buy the competing brand because it's cheaper. Now, someone eventually sells a PC with both USB and PS/2 ports so you can slowly start the upgrade trend, but it's slow for all the above reasons.
Same for the floppy drive: nobody wants to be the first to ship without one. It would be seen as being "too different" and cause lost sales to the competition.
Then comes Apple with the iMac and its all-USB ports and no floppy. You want an iMac? You're getting USB. You're getting no floppy drive. There's simply no choice about it. There's no competition, either, and Apple is already known for being more expensive so that's not even a factor. Apple decides they want to push the standard forward, and frankly you have no real choice about it (if you intend to stick to Apple).
Then the market opens up (for USB) or perception changes (it's OK to not have a floppy drive) or Apple defines something cool that people copycat, and in all cases Apple's marketing engine claims credit for changing the industry. Repeat something enough times and everyone starts to believe it...
And, to be honest, there's also lots of confirmation bias going on.