a term I just made up, and may not correspond to something in reality
The fear is that there are a bunch of hiring fiefdoms, all waxing and waning, so that I have to spend a bunch of time on a bunch of them to stay relevant. I don't want to be laid off one day and then find out that these days employers are using StackOverflow scores or wherever and that I should have spent the past year working on that.
OTOH, if 1) I can easily find out that SoftwareCo is hiring through Foo-CTF without having built a Foo-CTF profile, and 2) I can spend, say, 5 hours building a profile at Foo-CTF and get a serious response at the end of that, that's good. It means instead of spending 5 hours doing the silly technical interview dance with SoftwareCo, I'm spending 5 hours doing the serious work-sample test with Foo-CTF. Foo-CTF's value-add is that they're experts at doing the work-sample test.
This fear is unplugged from the reality of recruiting incentives.
It is in the direct financial interests of companies to recruit you directly, not through us. To recruit through us, they have to pay for the privilege.