I don't think medical research testing is necessary on animals prior to using on humans, the same as cosmetic testing on animals isn't necessary but the only reason I think they do it at the moment is because it's the quickest and least expensive to the human pocket.
We can resurface murder cases from fifty or more years ago using the latest DNA and forensic procedures but we don't know how to test a man-made drug using only man-made technology instead of on a defenceless creature.
I think the only choice these labs make is how little can they spend to get the maximum payback.