They removed it for shares too. Shares were always restricted a bit differently, but either way, features for tracking were removed there as well. On top of all that, Facebook released a new Platform Policy which made incentivizing Likes/Shares in any way a big no-no. That was always a bullet-point in their policies, in all honesty, but they gave tools that allowed it and seemed to look the other way. With the changes they made, they pretty much came out and said, "Don't do it and don't try to get around it".
developers.facebook.com/docs/apps/examples-platform-policy-4.5
I hope that helps explain,
Alex