Looking around the platform this morning I realized it ... almost all of our musicians are percussionists.
There's the drummer - obviously a percussion instrument.
There's the pianist - which is actually a percussion instrument, even though many think it is a string instrument).
Bass and guitar players, although technically string instruments, are really just like the piano and playing more like a drummer than a traditional string player (i.e. violin, etc.)
And for most of western contemporary evangelical worship, that's what you have. There's an occasional melodic instrument; however, it rarely plays what the congregation is singing. And in many congregations (if not most) these 'percussion instruments' are amplified and a lot of times the sound of the instruments drowns out the one to four vocalists.
The problem is that, in additional to providing a lot of loud percussion instruments, we are expecting the congreation to know (or learn) lots of songs without any aid to what the melody is supposed to be - other than trying to follow the lead vocalist.
And that often leads to a congregation that just doesn't sing out, or doesn't sing at all. Which then leads to non-musician church leadership trying to determine why the congregation isn't participating in worship, which often leads to replacing the worship leader, but doesn't deal with the problem.
The piano (and other 'percussion' instruments) are great accompaniment instruments, but are not designed to help people sing. They are designed to augment the singing. They don't do a good job of helping the singing process.
When the worship is flat on Sunday let's stop blaming the congregation (their hearts aren't in the right place), the worship leaders (for not picking the right songs) or the weather (too hot / too cold). Let's start fixing some basic musical issues and turn our congregation loose to worship with full heart and voice by removing the distractions that we (as worship leaders) are putting in their way.