One of them will be a team leader at some point. A second one might follow and become a team leader while the firth one goes higher.
Will they go up one more level ? let’s say yes. That makes e of them climbing the ladder.
Will there be a fourth ? probably not. That leaves 6 people not going up, and only earning marginally more. That’s less than half will see significant change in their 10 yers next.
Large organization graphs are shaped like pyramids, but the thing about a pyramid is that the combination of the top and the middle is as big as the bottom. The organizations large enough for unions to come into play have multiple layers of middle management.
But let's suppose the company is less than 50% managers. That still doesn't mean the typical person won't ever be a manager, it only means they're an employee for more time than they are a manager.
Also remember that small businesses employ the most people and don't have that sort of tree structure. In that case you typically have the owner and the apprentice who is expected to buy out the owner when they retire and ten person teams are not a thing. And you will often have some workers in larger organizations who don't move into management in the same company they started in but who do leave to strike out on their own, i.e. become a founder/manager of a new small business once they have sufficient industry experience.
Most people do not have a managerial position their entire lives - period.
There are indeed people who stay in dead end jobs indefinitely, but such people are not the majority of people.
https://www.bls.gov/oes/current/area_emp_chart/area_emp_char...
And those jobs often have less competition for those management positions because they're so often held by college students who go on to jobs in the industry they've studied rather than competing with other salespersons or fast food workers for the office manager position.
I've always found this condemnation odd given how often it's actually true.
If you break down salaries by demographics, one of the biggest correlations with salary is age. Senior positions pay more than junior ones. It's an extremely common career path to start off in an entry level job and ultimately end up in management by the end of your career.
So the reason people think they'll be making more money in ten years is that most of them will be. You may not be Warren Buffet but you could easily be the manager of your branch office and making two or three times your current entry-level compensation.