It's because mice weren't included in the Animal Welfare Act of 1966, while other major model organisms were. This made mice much easier to use, and then the wi

It's because mice weren't included in the Animal Welfare Act of 1966, while other major model organisms were. This made mice much easier to use, and then the widespread use of mice caused infrastructure to build up around supporting studies of them. It led the whole field into a deeply confused quagmire.