This is totally understandable, because in many ways programming is a "market for lemons": good programmers disappear off the market, there is a high chance you'll hire a bad one, and there is severe information asymmetry because it's so hard to tell how someone will perform.

But if it's true that good employees wind up in golden handcuffs, companies should advertise that! It's been several years since I've seen a salary that is competitive with freelancing, but if a company had a published plan about performance-based raises and could point to some happy employees who could verify that theory aligns with practice, I'd be more willing to consider their offer. Conventional wisdom is the opposite: the only way to get a decent raise is to leave. One obstacle to using high raises to attract talent is that a company would have to be more transparent about what salaries everyone is earning.