People here with shitty economic sense overspend using them and end up in debt. People with good economic sense use them for most of their transactions to get cashback/other benefits like bonus flights, etc. Some credit issuers also negotiate good deals with shops where you get the reduced price if you pay with their card.
We also use them for better fraud protection (liability shifts to the bank) and we usually get travelers insurance from the card issuer if more than half the price of the trip is payed with their credit card.
I'm in the UK, and we have to build a credit score if we want to get a mortgage, a loan, or any sort of finance, unless it's from somewhere predatory like a payday lender.