Except when research shows us otherwise.
This study, completed in India, used rewards to encourage better school attendance. They found it backfired. When the study was complete, the students either reverted to old habits or showed even less interest in good attendance. This study is not the only one of its type to show these results.
The sad thing is, rewards may work in the short-term, but in the long-term they can do more harm than good. If you are encouraging highly valued behaviors in your children, it is better if you stay away from rewards.
If you want your child to be a reader -- read with him and talk about books he is reading.
If you want your child to enjoy athletics -- play the sport with her. Attend her games and give her encouragement.
If you want your child to get good grades -- show him how to organize his day to give priority to studying. Recognize the good grades when they happen, but focus on the effort put in to earn them.
If you want your child to develop a habit of faith -- attend church with her on a regular basis. Read scripture together and pray together.
In the long run, intrinsic motivation, motivation that comes from inside, is not easy, but it is the best.
I will instruct you and teach you in the way you should go; I will counsel you with my eye upon you. (Psalm 32:8, ESV)