Why does the Airplay icon appears to the right of the play button briefly and then disappears?

[iMore Question]

After upgrading to the latest Windows iTunes this week, the airplay icon is missing from the radio player controls. More specifically, when I begin playing the selected channel, the airplay icon appears to the right of the play button just briefly and then disappears.

 

[mikeo007]

It looks like there are certain parts of the new Apple Music that can't be streamed via Airplay (Beats1 at least).
There's a discussion going on about it on Apple's official forums here: https://discussions.apple.com/thread/7104259