By that logic no one would test anything, who cares if mice feel pain as long as the testing could be helpful
Because we do not have the right to take animals from their natural habitats and abuse them. Just because t could help us does not mean that anything must die.
We have the technology to phase out animal testing; our computers can simulate everything to a high degree of efficiency, to the point where all you need is to test it on humans and see if it works (for medicine). It is more expensive to do so, but we can do this instead which will actually be more accurate than testing on animals and morally right as well.
how do we test things like how the brain matures
you can't get infants and toddlers to say yesbut there isn't zero scientific meritwhat else would we use
I don't think we need to kill infants and toddlers to see their brain?
Harmless experiments should not be outlawed at all; I am talking about the ones that are 'tests' and potentially can kill.
There is not much scientific usage in "if we kill 500 mice, will the other leftover mice be scared?".