Some people aren’t eligible for credit cards.
Some people aren’t eligible for cards with cash back.
Some people prefer to avoid credit cards as a matter of financial discipline.
Some people use debit cards to help small businesses avoid percentage-based card fees.
Some people use debit cards to conveniently get cash, which is the point of this thread.
BTW not many people seem to know that debit cards also have fraud protection by law, but it does require card owners to be more timely in reporting fraud than for credit. Some card issuers have additional fraud protection, for example Visa has 0% liability for debit cards except when processed by a third party.