Shrinkage in large carrying beams can cause one part of a house to settle more than others, causing drywall cracks and other problems.
Using flush beams with hangers, or engineered lumber or steel, can reduce the potential for shrinkage problems. But if dimensional lumber is hung flush from a beam made of steel or engineered lumber, the result can be a bulge at the beam, as shown below.
For more on working with framing lumber, visit the JLC Field Guide.