The old cylindrical mac pros had a similar trick where the case had a magnet in it and the computer itself had a detector for it. So if you ever wanted to turn it on without the case to see the diagnostic lights, you had to know where to put a magnet to fool the sensor.

This is an exceptionally overpriced way to do it: Dell PCs tend to just have a little push switch that's depressed when the case side panel is on. (For a corporate environment, these are also very helpful for tamper protection, of course.)

The key difference is that apple cares what their computers look like when they're open. Dell doesn't. An ugly switch would ruin the line of the Mac's case and look out of place.

Now, you may disagree with that philosophy, but Apple is wildly successful for it. Personally, I don't like Macs anymore, but I do absolutely respect that attitude.

I think removing the side panel would ruin your Mac's look more than a hidden switch behind the side panel does.

Apple believes that even when the computer is open, it should look good. Thin Steve loved joking that the back and insides of his computers looked better than the front of the competitors.