If you want to make the case that being less conservative will be better in the long run, you have to make the case that you're definitely on the right track, and doing it in a riskier way will speed up the eventual solution. You might accidentally go down the wrong path full steam and cost more lives, or just plateau in a dangerous way.

If I offer you an untested unreliable cancer cure, on the grounds that moving slowly kills more in the long run, I'm likely to make things worse by putting out a non-cure. We could do some really fucked up human experimentation to save more lives in the long run, but that's not the ethics we've collectively agreed on.