Why invest in your relationship with your partner today when you can work a little bit extra in the office?
Consider the hypothetical: My partner has health issues that requires me to earn more money to support us both/cannot work. Or I need to earn more money to pay for daycare/college for my children. Or my field is very demanding and also job prospects are slim, so I need to work longer and harder than average to avoid being laid off during the next restacking.
Some more familiar hypothetical: I work at a startup and if we succeed my partner will be set for life.
Why wait to pay for a phone in cash, when you can put it on your credit card?
Consider this hypothetical: I don't have the cash, ever, but I need the phone to get a better job so I could pay off the debt I enter when investing in a phone.
Why go to the gym when you can go drinking with your friends?
Consider this hypothetical: Due to working 12/14/16 hour days normally, I can only see my friends when I go out drinking with them on certain days of the week. My job is extremely stressful and my friends are my only emotional support.
Essentially, I'm not impressed by the reasoning displayed here. It's a general advisement that does not contain enough nuance, or even the option of a more nuanced life context.
While this advice suits a minority of people who are well-off enough such that they have stable, long-term gainful employment and enough time/resources to plan their lives, I would suggest an additional nuance that there are contextual situations that justify behaviors against the traditional short term vs long term sensibilities, in the same way that there are contextual situations where getting a codebase to work should be prioritized compared to getting a codebase to function in a readable, clever, efficient, well-thought-out architecture.