There's a very good reason why it is that way. A cable that carries data, like the one that goes from your house to your ISP can only carry a certain amount of information per time unit before it reaches its maximum capacity. By delegating less speed to upload, the ISPs can offer more speed for download. And since most Internet users use the internet for a few select tasks, all for which download speed matter the most by far, it's a sensible trade-off. Tasks such as web browsing, receiving e-mails with huge attachments, and downloading files all rely heavily on download speed.
Close - It's more to do with the fact the Upload frequency spectrum is alot smaller then the download frequency spectrum
Well, that's exactly what I said. I just didn't use quite as technical terms. I said that the cable has a limited information capacity (that would be the whole upstream+downstream spectrum in your graphic) and I said that the ISPs delegate more speed to downloads than to uploads. (that would be the reason why the upload spectrum has been made smaller than the downstream) I almost brought up the stuff about the frequencies, but I decided to go with a more "layman's version" instead, because I figured it would be understood by a broader audience.
