Why? Because PDF sucks at “future”.
Last week the Wolfram Group came out with its new file format named CDF. Well, isn’t that, wait … yes, that’s very close to “PDF” and I suspect the Wolfram Group was anxiously seeking for that proximity. For various reasons. I am not going to elaborate on that aspect, but I guess Adobe is as eager to earn money as is Mr Wolfram and his company. And both may rightfully pursuit their financial well being. But they’re both led astray. Because: