COL adjustments are not labor supply/demand. You don't pay a high COL because you want a candidate from SF Bay Area (unless you have your office there). Companies pay a lower salary in lower COL areas (relative to their target salary), because they have an excuse to and can save money. That's just how it is, I've been on that side of the table. Senior leaders saying "We're not going to pay them the same salary if they're living in nowhere kansas!!"

Thought experiment: Get a job, then move to a higher COL area, do you expect a raise? No. Move to a lower COL area: Somehow we expect lower salary?

My experience doesn’t line up with most of what you are asserting.

Many companies do have reasons to want employees in high COL areas, e.g. to be closer to the office, closer to customers, or lower travel costs.

And it is not uncommon to receive COL bumps upward when moving to higher cost locations. It is advisable to do this so that you keep your employees happy and don’t have them jump ship to other employers that will pay more.

“COL adjustments” might be publicly described as COL adjustment but they actually have to do with supply:demand of skilled labor in those various regions. Kansas has low demand for skilled tech labor so companies can win with a bid that would be considered a lowball in VHCOL, that is all that matters.

The company I work for has a published map with pay tiers on it. It's all admittedly a bit arbitrary and they are always careful to repeat often that employee pay does NOT scale with nor adjusted for the cost of living in your location, or inflation. (Basically to communicate that all raises are given based on merit and performance alone.)

Nevertheless, the highest tiers on the map are of course on the coasts, with mid-level tiers being parts of Colorado, Texas, Florida, etc. And the lowest tiers reside in flyover country where I live. But they say if you DO move permanently from one tier to another, your pay will be adjusted accordingly.

I’d make an even broader generalization, which is that all of these attributes are proxies for status. Graduated from a top school? Live in the Bay Area or NYC? Did well in High School (I guess?) These are all status indicators in the mind of someone higher up, and deserving of better pay. If you live in a low cost of living area it’s correspondingly lower status and deserving of lower pay. Other common status indicators include things like age, gender, and race…

My engineering team is split between Malmö and London. We’ve had people transfer from Malmö to London and they have received a COL raise. The reverse is also true.