23andMe sells the data, that's where they make the most money out of the deal.
Google makes $40 Billion USD selling the data it collects from the cookies it leaves in your browser.
Insurance companies are keen for the data they get from the DNA collecting companies. They have data banks of all the markers for serious genetic diseases such as cancer or parkinsons eg, which they will match up to the profile they purchase on you, and if you have it, they'll deny you insurance.
Nobody could pay me for me to volunteer my DNA, even though I know it's been stolen.