keeps surprising me that, in a time where everybody seems to be concerned about privacy, people willingly "give away" their dna profile...
I think it's important to remember that people can say one thing and intend to act in accordance with that, but do otherwise out of ignorance. Of course, however, that's not always the case.
True. Progress in that area can be a factor. I know some people who understood right away the risk from submitting DNA and some people who took time to absorb it.
Alternatively, it can be 2 different people. I know people who dismissed the risk as inconsequential. The folks I'm thinking of also maintained eagerness to aid LEO.