What has happened to Melodies?

I listen to music these days and although I really like most pop music and rock, it seems like most melodies are poorly put together. They don't flow. I know that part of this is because the main driving force in popular modern music is the beat. I am a big fan of the Beatles. One thing that set them apart from most bands was their great melodies. The melodies were flowing and pretty easy to sing. They also had really well put together harmony. I have studied music theory on the college level. I have studied and played classical music since I was twelve. What I have learned is that there are certain leaps from note to note that are actually expected by most ears. There are some that can make a person cringe. It seems like there are very few people who really know how to come up with a melody that makes sense to the average ear. I believe this is what makes most pop music almost impossible to sing A'Capella.
So now I wonder what has happened to cause the modern music writers to leave these patterns that most ears think of as logical? In the churches of Christ, we only sing a'capella and I see this same problem in new hymns. I think that most of the new hymns are written in the "pop" style and it just doesn't work when done without musical instruments. After I graduate with my degree in Music Ed, I plan to write new hymns for the church that are easily sung, beautiful, and scripturally sound in their message.