Or the RFID chips on their spools.
They do quite a lot of things that are fine atm but are gateways to giving them a huge amount of control if they every want to flip that switch - like if they get brought out or their investors start wanting to squeezing them for all they are worth.
Plus this applies to your family as well. DNA is shared and by you giving it up you give up info about those related to you as well.