So it's kind of a prisoner's dilemma. If you're a company and you invest heavily in junior talent, they'll probably leave for greener pastures ASAP. And if you're an employee who stands by an employer who gave you an initial leg up, you'll probably get fired after an aquisition/re-org/etc, and you'll find yourself with very narrow work experience.
FAANG companies manage this with "golden handcuff" stock vesting schedules, where you'll leave 6-7 figures on the table if you ever walk, but that's kind of the problem. It's hard for small orgs to compete for decades on pure cash compensation, and they can't be trusted to provide stability for decades.
Tinder makes it too easy to switch partners when the sexual marketplace values change, and it's the same for job hunting: it's just too easy to do for both parties.