This is only because companies don't want to raise salaries as engineers' skill levels increase. If companies put junior employees in higher salary bands as their skill levels increase there wouldn't be a problem.
Capitalism and fiduciary duty prevents employers from paying people their market value when they are content enough to stay.
An employee who does not do the effort to re-peg their labor time to market rates for their skill level is implicitly consenting to a prior agreement (when they were hired).
That is an extremely short-sighted view on what is essentially an iterated game where the domain knowledge employees have drastically increases their value to the company over time.
Sometimes because the company investors are overwhelmingly short-sighted, which IMO ties back to the whole "financialization" of our economy into a quasi-casino.
I wonder how things might change if short-term capital gains tax (<5 years) went way up.
When I started work (this was in the pre-consumer-internet era), job hopping was already starting to be a thing but there was defintely still a large "old school" view that there should be some loyalty between employer and employee. One of my first jobs was a place where they hired for potential. They hired smart, personable people and taught them how to program. They paid them fairly well, and gave annual raises and bonuses. I was there for about 8 years, my salary more than doubled in that time. Maybe I could have made more elsewhere, I didn't even really look because it was a good environment, nice people, low stress, a good mix of people since not everyone (actually only a few) were Comp. Sci. majors.
I don't know how much that still happens, because why would a company today invest in that only to have the employee leave after two years for a higher salary. "They should just pay them more" well yeah, but they did pay them in the sense of teaching them a valuable skill. And their competitors for employees started to include VC funded startups playing with free money that didn't really care what it cost to get bodies into the shop. Hard to compete with that when you actually have to earn the money that goes into the salary budget.
Would the old school approach work today? Would employees stay?
An employee who does not do the effort to re-peg their labor time to market rates for their skill level is implicitly consenting to a prior agreement (when they were hired).