Having worked in public and private labs that use animals for research there's a conflict of interest in minimizing the number of animals used and staying employed.

It is true of all jobs that if your project(s) get eliminated then your position risks getting eliminated as well. It's difficult at all levels of an organization to kill a project when so much work and money have gone into it, but it becomes especially problematic when more animals undergo experimentation as the project drags on.

I've seen animal experiments that have not given the results hoped for and were repeated numerous times with varying permutations (breed of mice used, age of mice used, sex of mice used, changing dosage, adding various cofactors etc...)

And while great medical break throughs have been made (especially in cancer research) by sacrificing animals instead of humans it is this aspect that makes me suspicious of the number of animals used.

Having done work with animals in private and public universities, one thing that always constrained the number of animals we wanted to use was the budget. At $20-90 each plus daily housing charges mice can quickly drain a lab's research budget. Maybe other ethical concerns should have been more important but ultimately money makes the world go round and money says "use fewer mice."