There's an excellent interview over at ChristianityToday.com with hymnists Keith and Kristyn Getty. In the excerpt below they note the two aims of their hymn-writing: sound doctrine and ease of use for diverse congregations (emphasis mine).:
I believe these are excellent principles for worship in any church, but particularly evangelical churches that have in the past 25-30 years seen a song repertoire that often lacks theological substance by downplaying or avoiding matters such as God's holiness, our sinfulness, God's judgment against sinners, God's mercy towards us in Christ, the atonement, Christ's passion and resurrection, and eternity.
Why the emphasis on doctrine?
Keith: I'm a child of the modern worship movement. We both are. I have a great affection for both modern worship music and traditional church music. I wanted to do two things. One was to write songs that helped teach the faith, and the second was to write songs that every generation could sing. I don't think of music as only teaching, but I do think that what we sing profoundly affects how we think. It profoundly affects how we feel. It affects, therefore, our emotional and our didactic relationship with God. But what we sing is for people of all ages.
The radical thing is that in the Old Testament, everybody came together and sang. And in the New Testament, the Jew and the Gentile, the Greek and the Roman, the young and the old all came together and sang together. That's the witness of church history. It's not some kind of food court where everyone chooses their favorite music and goes that direction.
I don't for a minute think that what I write will become everyone's favorite. That's just nonsense. The radical thing about a church service is that people of every age and every wealth bracket and every background come together and sing together. So we write these quasi-folk melodies that everyone can sing, and we hope there's an enduring quality to them.