Analogs of hemidesmosomes are the focal contacts described, which are also sites where the cell attaches to the extracellular matrix. These junctions are prevalent in fibroblasts but largely absent in epithelial cells. On the other hand, hemidesmosomes are prevalent in epithelial cells but absent in fibroblasts. In focal contact sites, intracellular connections are made to actin filaments, whereas, in hemidesmosomes, connections are made to intermediate filaments. Why do you suppose these two different cell types attach differently to the extracellular matrix?