I can’t emphasize this enough: with the exception of big-ticket items like cars and houses, don’t buy stuff you can’t pay off immediately.
I mean, I generally agree, but I could see financing a phone this way. I could probably buy a new Apple Watch outright or put aside some money each paycheck to get a new iPhone, I make enough. But it would take up most of my discretionary spending to buy a new Apple Watch. With this, I could space it out across three paychecks and reduce the impact on any one pay check. Basically, since it’s a 0% interest loan, it’s essentially the same as saving the amount of the payment from each pay check, but you get the item at the beginning of the period instead of the end. That could be useful when buying something that may be supply constrained when you have the money saved up, like this year’s model of iPhone. (And once it’s reported to the credit reporting agencies in the future, that means it’ll build your credit score, making it easier to take out loans on cars and homes.)
Also, I want to clarify that the big ticket exception doesn’t mean you’re free to buy more car or more home than you need or can afford. That’s generally as much of a mistake as (if not more than) the over use of consumer credit.
Also, another caveat: if you have financial discipline enough to never outspend your earnings and to pay them off regularly, credit cards can be a great way to build credit worthiness (and take advantage of credit card companies’ incentives, like cash back and free extended warranties or free travel insurance).
If you’re lacking in financial discipline, though, you should really only borrow money to increase your earning potential. Student loans are a good example, but try to make sure you don’t buy more education than you need (ie a higher degree or more prestigious school than you need to get a job in your field) for the line of work you’re going into, and try to make sure you’re going into a field where it’s realistic to pay off those debts*. Borrowing money to start or expand a business is generally a good idea, assuming you can afford to pay the terms back using the money from the business.
* For instance, it’s probably not a great idea to go into over $100k of debt to get a bachelors degree and a Library Science master’s degree if, realistically, you’re going to end up earning $30k as a librarian in a small city’s library.