This is where you need to not worry about what others do and you do you.
Whether or not they've thought about it, they're taking a risk by taking on credit and for a certain percentage of those, it will cause them stress and financial difficulty if things go wrong.
They're also committing to needing to work to service their spending/lifestyle. For most people, unless they've hit the utopia of earning a lot of money for doing very little or set up a passive income, which is unlikely if they've always spent all their money, if they don't work, it all comes crashing down fairly quickly.
Of course, it's unlikely that you know the true picture of anyone's financial circumstances except your own and the image they present might not tell the whole story. It might all be on credit, but it's interest free and actually making them a bit of money because it's backed up by savings earning interest. They might earn more than you think, have received an inheritance, won the lottery, sold a business, etc etc. I have a relative who retired at 40, but casual acquaintances won't know is that she had a serious accident at work, suffered years of pain and was left with a disability for which she received a significant amount of compensation, which has been invested to provide an income as she cannot work in the sort of field she previously worked in and isn't really qualified for work she could do.
As for your spending, you need to think about your eventual aims, which is usually being able to retire with an income that allows them to have the lifestyle they want without needing to work for it. Every penny spent rather than saved, pushes that date further back. But once you decide you have 'enough' there's also the concept of 'die with nothing' ie don't leave a huge amount of unspent money, otherwise, you've missed out on life. Obviously that's a difficult balance, based on unknown events, so the best you can do is aim for financial stability and once you're in that position you can spend a bit more freely. The financial flowchart sets out an order for this, which might be helpful.
https://ukpersonal.finance/flowchart/
The other point is what you do with your money. There's a huge amount of 'lifestyle' spending that can cost an enormous amount of money where you have to think 'is this worth it to me' and 'is it good value for money'? Because we make many many decisions all the time that can add up to a huge difference in your financial stability. People can spend hundreds of pounds a month, which is thousands a year or tens of thousands a decade and that's when it really shows in how some people always seem to struggle where others have savings and feel comfortable. It's not that the people with savings had more money, they just spent less and saved some.
Even lunch and a coffee a day vs free coffee in the office and leftovers from home can be a difference of £10 a day, so £50 a week, £200 pm, £2000 per year. And that's just one example.