I get it, but
It's hard for me to see from a strictly scientific perspective how an instrument that could detect alien life never seems to make the cut.
I believe it's more about long term funding. When Viking failed to detect life on Mars it killed the Mars exploration programs for decades. Since then NASA has been hesitant to do anything that could cut their long term piggy bank. So now the best we can ever do is keep looking over and over again for "the conditions that could support life."
Annoying AF.