Sure, on an absolute basis, someone who started with more than me will end up with more. But why does that matter to me? I only have my current resources to consider.
We all have some resources at our disposal. Understanding that slowly growing them over time can really add up is helpful regardless of where you start. In fact, I'd argue that knowledge of compounding is more helpful for those with little. Wealthy people aren't in need of more wealth, so the concept is less useful for them.
Habits are hard to break, it’s important to seed good ones.
Saving that $300 puts you in a better place than someone who squanders all of their cash. When I was starting out at work, nothing irritated me more than people bitching about how underpaid and poor they were, who somehow found the cash to burn up their earnings in cigarettes and to be out drinking all weekend.
We all have some resources at our disposal. Understanding that slowly growing them over time can really add up is helpful regardless of where you start. In fact, I'd argue that knowledge of compounding is more helpful for those with little. Wealthy people aren't in need of more wealth, so the concept is less useful for them.