I've noticed that too and always thought it was strange. I figured it's like that because they seem to prefer making KDF doff assignments harder to succeed at.
Examples: There are at least a few doff assignments that have "Extreme" casualty rate. I posted here on the forums a possible bug where 1 particular KDF holiday doff assignment had no traits whatsoever and a low default success rate. You can't even increase the success or critical rates and lower the failure/disaster rates no matter what quality doffs you use because of the lack of traits.
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Examples: There are at least a few doff assignments that have "Extreme" casualty rate. I posted here on the forums a possible bug where 1 particular KDF holiday doff assignment had no traits whatsoever and a low default success rate. You can't even increase the success or critical rates and lower the failure/disaster rates no matter what quality doffs you use because of the lack of traits.