bio people are not frequently math people and vice versa. The undergraduate departments make fun of each other. This is changing slowly. I suspect that a big part of the reason is that biology is complicated while math is good at dealing with distilling the behavior of a few essential elements.

When you start to find essential elements, they get mathified (look at DNA) but look how much experimental work it takes to do that? Scaling up experiments can also take some math, but once you figure out the trick, you just have a lot of experiments to run....