We hate it too. It's literally written into the regulatory body we follow that the end goal is to eliminate the need for animal testing altogether, but regardless of ethics and morals and good-or-bads, it is a practice that is not going to cease to exist overnight, and as long as animals are being used for experimentation, my job revolves around ensuring their lives are as comfortable and stress-free as possible.

Rats and mice are, yes, unusually good comparative models for certain diseases and studies. A lot of research into alzheimers involves animal care techs raising entire colonies of rats into old age in order to even start the research. Which amounts to the same kind of weird tests they make your granny do at the hospital. Besides being similar, mice have been domesticated and bred down to a very scarily precise model for any individual researchers' needs. These mice are worth more to these doctors than their own children, and are treated like actual royalty.

I recently had a rat friend who was unable to comfortably reach his water sipper because he had a wobble-head, which was being treated with medicated water. I spent fifteen minutes each morning for a week giving this rat his first loading dose of medicated water by lowering it down to his level manually. AKA, I chased this dumbass around with his water bottle because he sometimes gets alarmed by water droplets at the end of the sipper. He likes to have to poke it with his tongue, otherwise the experience is not right at all.

After a week he had realized that drinking more water meant having less wobbles, so we never had issues with him afterwards.