Lots of parents I work with don't want to reward their kids for good behaviors. They say, "Should I really have to reward them for things they should be doing anyway?" I understand their point.
However, rewards don't have to be used forever. When your child is 12, you won't still be giving him a sticker for using the potty (hopefully not anyway). A reward system should just be a strategy to help reinforce good behaviors that your child is struggling with.
Once your child has mastered a skill, you can back off on the rewards. Think of a reward system as just a little extra incentive for a short period of time.
Rewards also don't need to be extravagant. Use a sticker chart with preschoolers and it will likely cost you only a few dollars. Offer kids simple rewards like a trip to the playground and most of them will be happy with that.
So yes, when kids need a little extra help mastering a new skill, reward them. Then when they have it all figured out, you won't need to provide those extra incentives anymore.