Belief in angels is comforting, even though there is no proof for their existence. Angels can also serve as monitors of behavior. A parent can try to control a child's behavior by convincing the child that someone is always watching him or her. The angel is presented as being a kind of bodyguard, but the child will hopefully realize that the angel is also keeping track of all deeds, good and bad, even those done when mommy and daddy aren't around.
As a child, I was introduced to the world of angels and devils. The evil ones were everywhere, but the only angel I remember was my guardian angel. That one angel was enough comfort to ward off any despair from being in the company of too many devils. The guardian angel is a wonderful concept and has been adopted in many myths and movies; though in the movies, the guardian angel is usually transformed into a superhuman master of occult powers. Somehow, a bodiless, translucent, winged spirit in a gossamer gown wielding a laser sword isn't convincing. The angel is still popular, though, as evidenced by the recent publication of several books by "experts-by-experience" on the subject and the popularity of the television program "Touched by an Angel".
Why are these bodiless beings always depicted as humans with wings? Because depiction enhances belief and a bodiless being cannot be depicted. We can imagine a non-bodily being only by suspending our belief in reality as we know it. How does a bodiless being think or feel? To talk of spirits as non-bodily beings is to utter words without any more meaning than the expression "round square".
See entries for astral projection, mind and souls.