Good point! I sometimes ask my kids to do something for me in exchange for a reward and when they ask what the reward will be, I replied, "Kiss from Mommy."
At first, they thought it was a silly joke but obeyed anyway.
Now they would offer me help and asked me for a hug or kiss as a reward, it is because they're happy to please mom.
And that's indeed a good reminder to us parents not to spoil our children with material things :) thanks @ysolina