I got my degree in psychology. (And while I don’t have children, I’ve had 35 years post-degree to see how this has worked relative to how I was brought up) What you are talking about is essentially operant conditioning.
The issue when attempting to use operant conditioning in the form you are describing, is that rewards or punishments that occur closer to the behavior are stronger than rewards that are more removed in time. The other issue is that people place different values on different rewards and punishments.
Note: I have ADHD-PI, and I’ve attempted to use operant conditioning on myself for years to improve habits, with mixed results.
Let’s take brushing your teeth. The consequence of not brushing your teeth is cavities and bad breath.
But, no one really experiences their own bad breath. Cavities don’t impact a person until you go to a dentist (getting a filling) or the tooth is so far gone that you are getting a toothache. Thus, at best, cavities will not negatively impact a person until at least a couple of months of not brushing teeth occur.
Meanwhile, brushing your teeth has immediate negative consequence - at best it’s boring. Toothpaste can have an unpleasant taste and texture. It’s keeping a person from doing more pleasant things like gaming or sleeping.
To establish a good tooth-brushing habit in your child, you’re going to have to fix the immediate negative consequences - make sure they like the flavor of the toothpaste, or at least don’t actively hate it, and engage with them while they brush their teeth, or make it a game while they are young. Tell them their post-brushing breath smells good (positive reinforcement).
Adults have a hard time responding to delayed gratification when there is available immediate gratification.
Children, for whom a couple of months is a much bigger chunk of their life in comparison to your life, are going to be abysmal at delayed gratification.
If you rely on rewards/negative consequences that only occur after extended periods of time, what you will find is that those rewards are not very effective.
The second issue - placing different values on different rewards.
When I was having problems in school, my parents took me to a place in Fort Worth that specialized in childhood problems. The therapist I saw did not diagnose me with ADHD, but instead “the worst case of passive-aggression he had ever seen” (I hope he had worse problems with his own children.)
One thing he recommended to my parents (which I don’t even remember this happening) was to reward me with money when I did something right.
Didn’t work. Money didn’t mean anything to me.
What did work was a couple of years later my parents decided to let us choose places to eat when we did well on our report cards. Best grades I got for my entire school career was the year they did that. What they were rewarding us with was control - which was probably the thing that, as the youngest, I had the least of otherwise.
Another big possible reward that a lot of parents don’t realize is the reward of attention. Take a kid that is always acting up, and there’s a good possibility that they need attention, and that is the only way they will get it, or possibly the only way they know how to get it.