Depends on the type of gig.
A jazz gig i where people come to hear musicians play instruments at a high level. Or a concert or even a bar gig where people came to see/hear a band play. Or the prevalent acoustic guitar player singesr all aroudn here on the bar decks. They see him strum 4 chords and sing so something they can see is happening.
A party or casual get together or even a dance club? No one cares how the music comes out as long as it sounds good and they can dance to it. It can be a DJ or now a DJ who sings. Same thing, no one cares. They focus on the vocals. I've seen it numerous times.
I'll relate just one example. A good friend back in NJ used to do a keyboard / vocal / DJ thing. He stopped bringing the keyboard and now stands up and just sings to backing tracks. Uses two Ipods. He's still doing the same parties and restaurants he did before for the same money. Go figure.