Let's start with the fact that Hoagy Carmichael had a nickname rather than a stage name. Then, consider some of the characters who appeared in his songs: a poor washerwoman, a little boy playing hooky, a little old lady in a rocking chair or window shopping on the town square, a guest at an upscale party, an opium addict. Every one complex. Every one nameless.
True, he sanded down and varnished their rougher edges. Maybe it was done in the service of introducing them to far more people.