Since I only take jobs where I have total control of the music, I have not yet heard a reason to go instrumental only. I will, however, have my wife monitor the clarity of my voice compared to a lead instrument. Obviously a shrill trupet will cut through chatter better than a baritone voice, or so it seems.

My thought is that many songs should be sung to include the lyrics, which is undeniably an integral part of the song, and, add immensely to my variety. As far as ability is concerned, I have sung for many years, and consider myself good, but not great.