Secondly, who ever gets fired for asking for a raise? I mean, that is not normal. And if that does happen to you, it's most likely of some other underlying factors, where asking for a raise is just the last drop.
An alternative perspective from my time managing: That reflects the viewpoint of the business, not necessarily the viewpoint of the manager.
Getting an out-of-band raise approved triggers entire internal processes, outside of the control of the immediate manager requesting it.
Triggering one proactively as a manager with no impetus other than "this person deserves it" is likely to get denied or a token amount approved. As you said, the business wants to pay the least amount of money an employee is willing to accept. If the employee has given no indication they have issue with their current pay, the business has no reason to presume there's a need to pay them more.
However, once someone asked for one, I could take that and use it as leverage. If the employee has brought it up, there's evidence of doubt on whether the company is still meeting that minimum threshold. Denying the raise outright increases the risk of attrition, so the business takes it seriously compared to the proactive request from the manager. Then I can use what I know to work the system in the way that results in a far more favorable raise.
I don't know - man. I've worked at a lot of places and this doesn't seem to be a common thing. It could be I've just worked at a lot of bad places but still. Asking for more isn't enough. It has to be the threat of leaving in order to get them to give more. At which point - the advice now for managers is, if they're threatening to leave unless you pay more then just let them leave.
* If you’re indispensable, the rules may not apply to you
The reason I ask this is because every time I've asked for a raise I've been underpaid relative to the market and known it, and been able to walk into a meeting with a list of numbers recruiters have sent me and credibly state that I'll have to consider other options soon. I would be surprised to find this hadn't worked for someone else, and even more surprised to find they hadn't left.
It's not charity to pay people what they are worth, it's a good business strategy. Paying them the least they would accept is a sure way to have a high turnover and frustrated employees. Bad strategy. At least in a workers' market (so in IT for example).
Asking for a rise is awkward, many people have problems doing it, so they postpone it. In IT the expected salary growth is pretty fast, especially early in the career, and it's also the time when junior developers are the least used to negotiation with their bosses. So people are routinely underpaid until they talk with their friends and realize switching companies gives them automatic 10-15% rise and some new learning opportunities.
When you have a job applying for a new job is actually pretty stress-free, and it's a good idea to do this from time to time just to see what technologies are hot and what questions people are asking. Then you get offered 15% more than in your current job and a new project that always seems better than the project you're currently working on :)
So companies that don't give rises without being asked to - will have to deal with a high developer turnover and all the associated costs.
Perhaps in the tech industry where there is a lower supply of workers, but not everywhere. Plenty of managers will say no because they know you can be quickly replaced.
Not everyone is you/us.