Developers want more money for more experience.
At a certain point, more experience does not make them more effective developers.
If they want to justify higher salaries, but can not be more effective on their own, they need to multiply their experience by making other developers more effective.
The organizational problem is that most companies see management as the only way to do that, but not everyone can and likes to be a manager.
We as developers have to make sure we promote mentoring, tool and framework building, system architecture and such topics as viable paths upward. Otherwise, managers will only have managing as an idea of how someone can create more value.