It all depends on your needs. If you have a great researcher already and really need a crafter, then you don't really care if that downed raider with 9++ crafting can't do intellectual. You don't want him doing that anyways.
Similarly, if you need a researcher and find someone with good intellectual, it doesn't matter if he can't do dumb labor. He's going to spend 100% of his time in front of a research bench, so he won't have time to haul and clean.
But if you really need to get stuff hauled and your home is a total mess because nobody has time to clean, then picking up someone who won't do dumb labor might not be the best idea.
Then there are the traits that have effects other than skills, especially in certain combos. Do you really want someone who is abrasive and bloodthirsty, and will be causing social fights right and left? Or how about that neurotic pessimist? Sure, he'll work quick, but you'll be constantly struggling to keep him mentally intact. These sorts of bad combos aren't worth it, even if you need the skills they have.
Similarly, if you need a researcher and find someone with good intellectual, it doesn't matter if he can't do dumb labor. He's going to spend 100% of his time in front of a research bench, so he won't have time to haul and clean.
But if you really need to get stuff hauled and your home is a total mess because nobody has time to clean, then picking up someone who won't do dumb labor might not be the best idea.
Then there are the traits that have effects other than skills, especially in certain combos. Do you really want someone who is abrasive and bloodthirsty, and will be causing social fights right and left? Or how about that neurotic pessimist? Sure, he'll work quick, but you'll be constantly struggling to keep him mentally intact. These sorts of bad combos aren't worth it, even if you need the skills they have.