I like the description of the "Value Apex". I admit I haven't heard of that one before but it makes sense, and thinking back it's usually the reason I jump ship, and indeed is probably the way things are headed in my current company.

When you start at a company (and early in your career), you can add value Z, and get rewarded Y in proportion to your work/output X. Where Y is whatever motivates you, money, advancement, interesting work, etc. As you remain in a company, Y and Z tend to reduce over time sometimes even to zero, to the point where additional marginal work does not result in commensurate additional marginal value/reward. At that point you've hit your ceiling. You're stuck. If you have any ambition at all, you're headed for the hills, to a place where you can start expecting more proportional reward once again.

Some people don't care--they're happy to hit their position's ceiling, and just hang out there until they get bored. For ladder-climbers it's pretty much unacceptable.