That is assuming that everyone is a hired mercenary. I could rather easily find a job that pays me a 10%-30% raise over what I currently make. I don't do that because I already make "enough" and I like my current job, company, and coworkers. It isn't even a matter of loyalty, it is a matter of different priorities that puts money further down the list than job satisfaction. Finding a good paying job is much easier than finding a good job.
This is highly relevant. Looking for a new job is like another job in itself. You have to do research, have telephone conversations, be "switched on" in your interview persona for hours at a time, jump through flaming hoops, and if possible, also be younger, more energetic, and more beautiful than you really are.
It's a sales job, with you as the product.
I. Hate. Doing it.
So while a lot of people could go out and get a better, higher-paying job, there is a potential barrier and significant activation energy for that reaction. Doing my regular job plus the self-sales job is absolutely exhausting.
When my current job is already almost good enough to keep, I have little incentive to go sift through piles of recruiter spam and speculative postings to find the actual jobs, retype every last detail of my resume into yet another stupid custom candidate tracker web-app, suffer through the bozo filter and the pop quiz of the tech screen, fly or drive wherever, and spend one of my vacation days playing along with some stupidly involved interview process, only to see a curtain of silence descend forever.
For $30k, and an extra 40 hours per week in which to do it, I would certainly put up with the tech hiring circus for a couple of months.
Note that he said a good job, not necessarily a better one. I think the idea is that if someone is giving you 30k to find one, you really only need to find one that pays the same, or close.
Technically you'd come out positive if you found something that's at least more than (what you make) - 30k, but then you have to consider raises and such.
There's always a better job. At some point you have to stay somewhere for awhile, to gain whatever it is you're trying to get: stability, experience, improvement, contribution, pay, benefits, community.
Their current job might be "good enough" in that the benefits of switching are not significantly over the costs of switching. But when you add 3 months of salary to the equation, that might tip the scales.
There is nothing wrong with being a hired mercenary.
If you consciously attempt to hire true believers, then you will get two kinds of employees: true believers, and people who lie about true believers.
That set of employees is probably pretty small compared to the larger set of qualified employees without such a restriction. You write off a huge pool of talent.
Just because you're a mercenary doesn't mean you won't bring your all to the task at hand.
Also, consider the employee relationship from the other direction. No corporation is going to hire an employee because the corporation is a true believer in the employee's mission. That relationship is a strictly mercenary one: Can you do for us what we need you to do for us?
But if you weren't currently happy with your job and you weren't confident in the chances of that changing, it wouldn't make you a mercenary to jump ship at that point.