Works on challenges (intrinsic) --> gets new skills + generates increasing value for the company
Repeat this cycle for many moons and the worker now has a significantly upgraded skillset that has and continues to produce significant value for the corp. All that is asked is that the salary grows with respect to the skill set being utilized and the value being produced for the company.
If you end up in a situation where skill sets and value are increasing substantially but compensation is stagnating, you end up in a situation where people will eventually take a look around at the market and realize other people with similar skillsets who provide similar value are getting offers at a substantially higher rate (even assume inflation increase of 3-5% for several years, that adds up). Yes, the work might be challenging and the worker might enjoy the work intrinsically but extrinsically they're now asking whether pursuit of the intrinsic challenge is worth it given the disparity in how they're valued compared to their peers.
Pay isn't necessarily about the tangibles but more about how the company values you (scorecard). If your salary gets out of line with market by a substantial amount relative to skills, experience, and value generated, that indicates the company doesn't necessarily value you as much or isn't willing to expend the capital necessary to keep their employees satisfied.
The other angle one could take with this argument is that while intangibles are nice, they cannot offset the increase in price of other things like housing, and food. Without pay raises over time, the percentage increases in basic cost of living will eat into the paycheck more and more. Induced pressure from external sources can undermine intrinsic motivation, especially if there are dependents, and increase the importance of the paycheck amount.
