Singers are weird people. When they don't like the lyrics you've written for them they simply cut off the communication. You never hear from them again. That happened with Rastin, Katharina, Ethan, Yasmin, and now Fabio - so it doesn't seem to be gender-specific. I've written for guitar players who also sing - no problem. Kai didn't like what I wrote, and he said - or rather wrote - so. That's fine. Holger, Craig, Martin, Marian, or Stanislav take their picks - that's even better. Yet the 'vocals-only singers' suddenly seem unable to correspond. Well, Flamur actually sung one song that has my lyrics, but after that he kind of vanished into thin air as well. Is it cowardice? I've got no idea.
Now that I'm no longer restricted by the tune I will rewrite the lyrics I wrote for Fabio so they look and flow better as 'lyrics-only'. And I will ask future partners if they play an instrument or produce songs themselves. If the answer is "no" to both questions I'll forget about writing for them.