to take on more responsibilities and advance my career, I'm going to take it. That really doesn't change for me whether I'm 20, 30, or 40 years old (and I'm not going to be working when I'm 50+).

You can blame employees but underpaying for loyalty is a systemic employer problem. The reason is obvious, nobody likes change and interviewing is a hassle, employers bet the majority of employees will stick around because of the human disposition to avoid change. The issue is higher talent is driven and in a hot labor market they will vote with their feet.