I love singing, although I'm not what I'd call good at it- I spent some time singing in a band, and I've just recently been asked to sing background vocals at some of the shows I've been playing lately.
I've realized that not only do almost any form of background vocal help in a live setting, it also has big benefits for me, as well. Here's why you should consider singing at your next sideman gig:
1. Value Added
Band leaders love musicians that can sing as well as play an instrument, and will often think of you first next time they need to hire for a show, if they know you've got the ability to add something your competition can't.
2. Better playing
I know- how can you play and sing at the same time, and not be worse as an instrumentalist? It's not so much that you're going to improve your chops, but you'll be less tempted to avoid the cardinal sin of overplaying. Since you'll be forced to simplify your riffs during times when the singer is singing, you'll naturally fit into the mix much better, and not distract from the main focus of the music- the melody.
3. Less boring
If you're not overplaying, you're probably going to get really bored during sections of each song when you don't play. Singing is a great way to spice things up a bit.