This isn’t about income levels.
If you treat your credit card like a debit card, you’re in the same position with additional benefits
It isn't about income levels. It's about mindset.
The reason why credit card debt is the second highest consumer debt in the US is because not enough people have the mindset and/or ability to pay their balances in full every month. Some people do not trust themselves when it comes to spending so they will charge anything and justify it by telling themselves they'll pay it later. Generally speaking, people check their bank accounts more closely than their credit card statement and manage their accounts that way. Because of these reasons I cannot fault a person who still uses debit cards. Like you said, it takes discipline to responsibly use credit cards, and not everyone is responsible with their finances.