Why companies don't retain talent?

I can answer this from what I saw at Facebook over 8 years. I was an IC but I was involved in discussions around comp for internal vs outside engineers and talked to several execs about this. Facebook didn't do (from 2009-2017) retention adjustments. I won't talk about anything confidential, but just at a high level. 1. If you make offers to retain one person, it creates a precedence. Now other people are encouraged to get outside offers, or threaten to leave. Netflix has a culture that supports this idea, but many companies don't and they would rather have everyone 100% focused on work. 2. Fairness. If one or some people get some kind of adjustment, then their compensation might not be fair compared to similarly performing people who are not threatening to leave. At Facebook, fair compensation is the number one goal. It's almost impossible to pull off because of personal circumstances, timing, etc... but they try to have an "eventually fair" model and complex adjustment formulas over time to make things more fair. 3. The closest thing they have is "Additional Equity", at the time of the normal performance review cycle there is some wiggle room to give people critically valuable to the company additional equity grants. So 3 is probably the closest thing to proactively trying to keep top performers, and the middle road valuable-but-not-crtical person they are ok with them leaving.