They need some sun. It is possible that the area you see them in has had an increase in the canopy, and they are not getting enough sun to flower (but enough to keep growing).

Thanks for the input...that does make sense. We planted a sweet bay mag in full sun and it grows and flowers like crazy but when I find mags in the woods the canopy lets in little sun, hence no flowers. How do these things reproduce then?

the woods today are not the same as the woods when those magnolias developed. the magnolias will not be able to reproduce as prolificly(sp) as they did in the past... same thing is happening to oak trees in the midwest... fire no longer occaisionally burns off woodlands... the fire keeps the canopy from becoming dense. more understory plants can thrive in a open canopy than do today in the dense canopies that have evolved by mans fire prevention.