[Chromecast Audio] Why is it not possible to set a default Chromecast Device output?

[ldenninger]

I use my tablet(s) and Chromecast Audio to stream multiroom audio in my house.  

Every time I want to put on some music, the tablet starts playing music. I have to go to Chromecast devices. Pick my "Play everywhere" device. Wait a minute for it to connect. 

Then with a bit of luck after 2 minutes I'll have music playing.

Why can't I just configure Spotify to "Always output audio to this specific Chromecast device/group" ?

It shouldn't be hard to remember the output device/group, so why am I forced to select it time and time again?