Molecular biologists and mathematical models frequently don't mix well, especially when the molecular biologists in question were trained before the rise of genomics, back when most labs only needed a computer for designing new vector sequences, writing papers, and checking email. Behind this skepticism is the intuition that biology is extremely messy (true), and difficult to quantify (also true). Also contributing is the long history of the cell as a molecular black box; for a long time, we had no idea what was going on inside the cell in molecular terms (somewhat analogous to doing chemistry without knowing about atoms), and in fact we still don't know the molecular role of a good chunk of the protein-coding genes in the human genome.