Thread by @swardley

X : Why is it more difficult to get a job, if you don't have a job?
Me : Daisy Chains.
X : Eh?
Me : Recruiters like you to have a job, so they can plan to fill your job when they put you in the new role. They create a daisy chain of people where they all shift one role ...

... the recruiters make money on every shift. It has nothing to do with your ability / capability for the role, it's just if you don't have a job then you break the chain and are less attractive to the recruitment company.
X : But I could be the best person.
Me : And?

X : Surely recruitment is about finding the best person for the role?
Me : That's called marketing. There are a few (and I mean, a few) exceptions.

X : Why would any company work with them?
Me : Because they save your bacon. That time your lead engineer left and the recruiter found a perfect replacement in a few days ... well, they were making money on your lead engineer leaving and had lined up the replacement beforehand.

Me : They do that a couple of times and you suddenly think that they are your best friend who always helps you out when trouble hits.
X : That's very manipulative.
Me : You don't know the half of it.

X : How bad can it get?
Me : Well, in the worst cases, they "save" your bacon so many times that management start thinking they are essential and you get suckered into exclusivity arrangements. You've lost all control at that point.