It's because all of the bandwidth was urgently required to transmit the latest vital information about hollywood bimbos.
A few years ago, I attended a rather lame panel discussion in which AC Clark participated via shortwave radio. He did seem to be a bit in decline at that time, but still interesting to talk to. Anyway, he started his remarks by saying:
I'm afraid I've had some rather bad news. I've just been to the hospital for a check-up, and it seems that my blood type has been discontinued.
The recurring theme in his stories was dealing with transcendence. I find it curious that he so often chose to have transcendence imposed by mysterious external forces, but more interesting when people selected and engineered their own.