A salary is like RAM, you only notice if it's too little. Once you reach this comfort level where you can cover your expenses and feed your lifestyle without having to think too much about it, getting some extra will make far less impact than the number might suggest. Not having enough money is like drowning and you'd do anything for a breath of air. Having just enough to live comfortably is like getting to the edge of the beach. Moving further up the beach a bit is nice but you certainly won't be willing to break your back to get there.

It's not only diminishing returns at work but simply crossing that comfort threshold severely drops the incentives from "survival mode" to "eh... yeah... maybe".

And sure, if you like living just above your means you'll always be in "survival mode". Always the better car, the better house, the better vacation, they need to be financed and every little bit will count. I think that's not where most people are.