Modular grant level was set nearly 30 years ago, in 1998. A single modular R01 cannot support a research lab with mammal models, the LARC expenses alone will deplete the budget.
I don't think anyone has any idea of how thin the margins are in science. To have funding agencies or private foundations come back on a proposal and ask you to cut 10-20%, or more from a project simply means the work cannot be done. Modular grants have not been adjusted for inflation in >20yrs.