This is cope - managers repeat this narrative so they can blame some other factor rather than having to put in the work to fix the problem of hiring good FTEs. Unfortunately, this narrative has been repeated so often that it is perceived to be axiomatic, which is why it is repeated without any criticism.
No, its not that hard to find good FTEs, you just haven't tried hard enough, or you're not paying enough, or your glassdoor reviews are bad.
this is not a negligible barrier. Sure you could argue that a business that isnt successful enough to hire for that expensive FTE maybe shouldnt exist at all, but a lot more is possible by being able to outsource it. And there really isnt a good reason why it cannot be outsourced from an operations standpoint - it is entirely a security problem. It's not like auth is hard to do for a third party.
e.g. nobody got a promotion because the change they pushed for 5 years ago prevented an attack today.
That's not to say people are just greedy and only chase what gets them a promotion, but replace "promotion" with "received positive feedback".