- Your praise is valuable.
- By giving a sweet you are devaluing your praise (both to the child and yourself): they will learn to seek sweets and not praise.
- By making sweets something to work hard for you are increasing their perceived value.
- The child will learn to expect a sweet when they’ve done something well.
Penelope Leach summaries this well in her excellent Baby & Child book (page 309):
If you can keep sweets out of the emotional arena and treat them as coolly and calmly as you treat other particularly nice-tasting things such as strawberries or honey, none of this trouble will arise. Many children passionately enjoy strawberries and will eat as many as they can get during their short season. But how many of those children whine and cry and throw tantrums for strawberries?