It's hard to grasp, but singing is neither easy nor difficult. Well, to state that in a way that is closer to the truth, the act of singing is easy and simple, but the act of learning a song and singing it well is pretty challenging.
You see, the act of singing can be as simple as speaking - just making sounds like we do all day when we speak, except in singing we use a wider range of tones, notes and volumes (dynamics) - the thing is we also have to learn rhythm, feel, tempo and delivery and that's when things get complicated.
That's why vocalizing and singing have to be divided. When we vocalize, we connect with the simplicity and ease of making sounds, but when we sing and practice songs we incorporate the emotional dimension to the art of singing.
So contrary to what I might have said before, singing is not easy or hard... singing is a mix of both. The real conclusion is that it take a lot of practice, dedication, commitment, love, discipline and freedom to deliver the song with love in a way that can connect. Make no mistake, focus... which is hard for us humans is the main ingredient of the craft and art of expressing song.
May you be clear and committed to the fine art of SINGING!