In the worship band, I find some songs need the click track to keep everyone in time, especially if there's a pause in the song or a part that's not got a noticeable rhythm playing with it.
But then there's songs where we switch the metronome off after the count in & just play. The click gets in the way of the feel.
In my rock band, there's no click track. I was listening to some stuff we did last week & there's a few parts where even if just the drummer had a click, it would have made a huge improvement.