Echo speaker does not show up on iPad AirPlay list

I have an Amazon Echo Studio speaker. In the mornings, I often play Apple Music selections from my iPad through that speaker--but not via the AirPlay speakers list.

I choose something in Apple Music and hit play. It plays through my iPad. I touch the AirPlay icon and it brings up the "Speakers and TVs" list. But only my desktop Mini and my two Apple TVs are on it. The Echo speaker is not on it.

So, to get the music to play from there, I then go to Settings>Bluetooth>Echo Studio-1A and touch it to change from "Not Connected" to "Connected". When I do, Alexa says, "Now playing from Gary's iPad" and the music starts coming from there instead of the iPad.

OK. But why does the Echo speaker not just show up in my AirPlay list? Is there something I can do to make that happen?

(BTW, I can play Apple Music through the Echo via my voice. And Apple Music is my Echo default music source. But the Echo does not recognize the names of all Apple music selections, so that is not always an option.)