I wonder why he cares whether or not people delete their DNA?

I asked them to delete mine (although I'm not optimistic that they did so), and I'm glad that I did for two reasons. First, I don't think they dealt with me transparently and honestly from the start and second, whether or not that data is directly a risk to me, it's yet more data about me that's out there in the world and can be combined with other data to make a potent risk.

The less data about me that exists in any database, even trivial or apparently innocuous data, the better.