After college I got an internship as I had no prior industry knowledge. At the time this was fine. I was living back home with my parents and actually able to save. $14/hr was twice as much as I've ever made at my minimum wage jobs. After a little over a year I was hired into an exempt position for 20% more pay.
Five years later I was stagnant after repeated empty promises of promotion and more pay. I found myself one of the go-to people that leadership would ask for financial and tech questions yet I was paid far less than anyone I was sitting in meetings with. I was turned down for a promotion that fit my experience perfectly because they hired the VP's daughter who didn't even have a business degree or experience. I thought I was going to be stuck forever. Finally there was new leadership that actually cared about qualifications and I got the promotion I was previously turned down for.
Everything was good until I realized how much more the VP's daughter was making than I was. I figured I would be here forever stuck with my intern level pay as setting the stage for my entire career regardless of how often I was promoted. I finally had enough and I found a job that paid what I was worth.
Now I've been at three other companies since getting large pay bumps each time. I'm starting a new job next week since I didn't receive an increase during record inflation so I found a job that pays more. Turns out companies don't care how much company specific knowledge you have. Turns out none of that matters. Now I'll be contracted with my previous employer to help transition while making 3x my previous pay. Why do these companies love hiring outside people? I'll be relying on everyone else and it will take a couple years at least until I'm settled and actually know the ins and outs of the company. All would have been avoided if I got a consistent 4% inflation increase each year.
TLDR: Employers will pay you as little as they can get away with. Change jobs often and never wait for a promotion. You don't owe any loyalty to a company and loyalty will hurt you financially.