Gift cards fall into the category of extrinsic motivators, which have been around since the first hunter left food out to trap his prey. We get our kids to do their chores by offering them an allowance. We bribe students to read during summer vacation with the promise of a reward. It seems like a win-win.
But in the long term, there is evidence that extrinsic rewards do not always work as advertised. The biggest problem is a process called externalization. Extrinsic rewards are very good at capturing our attention. Unfortunately, they do too good a job. When we start associating a behavior with an extrinsic reward, it breaks any link there might have been to intrinsic motivators. In other words, when we start engaging in a behavior for an extrinsic reward, we lose track of the fact that it is “the right thing to do” and “good for its own sake.”