It also gives you points for doing this and ranks your activity against your friends, which is why some people get really into it.
Bill [Atkinson] fired up his demo and it quickly filled the Lisa screen with randomly-sized ovals, faster than you thought was possible. But something was bothering Steve Jobs. "Well, circles and ovals are good, but how about drawing rectangles with rounded corners? Can we do that now, too?"
"No, there's no way to do that. In fact it would be really hard to do, and I don't think we really need it". I think Bill was a little miffed that Steve wasn't raving over the fast ovals and still wanted more.
Steve suddenly got more intense. "Rectangles with rounded corners are everywhere! Just look around this room!". And sure enough, there were lots of them, like the whiteboard and some of the desks and tables. Then he pointed out the window. "And look outside, there's even more, practically everywhere you look!". He even persuaded Bill to take a quick walk around the block with him, pointing out every rectangle with rounded corners that he could find.
When Steve and Bill passed a no-parking sign with rounded corners, it did the trick. "OK, I give up", Bill pleaded. "I'll see if it's as hard as I thought." He went back home to work on it.
Bill returned to Texaco Towers the following afternoon, with a big smile on his face. His demo was now drawing rectangles with beautifully rounded corners blisteringly fast, almost at the speed of plain rectangles. When he added the code to LisaGraf, he named the new primitive "RoundRects". Over the next few months, roundrects worked their way into various parts of the user interface, and soon became indispensable.
Jobs did not create brand new designs and schematics and techniques out of whole cloth; he had his research staff to do that. His contribution was pushing the researchers in the right directions, pulling them back from going in the wrong ones, and enforcing a consistent vision and design strategy for the whole enchilada.
After a number of decimal places, nobody gives a damn.