Of course it's not a reason. Everyone knows the real reason is killing second hand market and making sure you can't even borrow your game to your friend.
yup that's the real reason, they know that far less than a tenth of people that pirate games would buy it if they couldn't pirate it. But someone willing to buy second hand at a $5 discount more than likely would. They are just trialling it on PC as they know PC gamers are more used to DRM and worth less to them, plus they can use piracy as an excuse. Other publishers are trialling other measures like EA's online pass.