We all have them.
My best friend is an interesting case-study, to me at least.
He is now 48, and we have been friends for 25 years. He spent his 20s stumbling from temporary job to temporary job, always struggling to make ends meets. During that time I used to outearn him, but to his credit he has always been an avid life-long learner. He put himself through an adult degree in his mid-late 30s, changed his career and has always improved his work-place skills every year I have known him, and now he is well qualified and experienced in his field and works contracts that pay handsomely, and while my income plateaued quite a few years ago he has increased his earnings all the time and I would handily guess earns triple what I do.
Despite, or perhaps because of his earning power, he's always reaching for the next step on the consumerism ladder and is never more than 2 paycheques from being in serious trouble. He works in London but they recently moved and bought a new house in St Albans.. I mean, that commute would already crush me.
When you have more money you tend to spend it. House & associated travel costs I have just illustrated... but it's anything and everything that tends to inflate. You use your income for convenience in each and every situtation you can think of. Instead of bringing in tupperware and leftovers for lunch you go to the restaurant and spend £20 every lunchtime. Hey it's "only" £100 a week.. right? Taxis whenever you need to get from A to B. Bigger car. Missus has a car accident you say? no problem, write it off, but a new car (Who wants a dent in their bumper.) etc etc.
He also doesn't have a pension or any other savings for retirement. I have "advised" him that he needs to change his way and find a way to live on half his income, but he is wholly incapable of spending less than he brings in, never mind drastically doing so for any sustained amount of time.
He will literally never be able to retire.