Recruitment Companies...

They are so varied in the way they treat potential candidates.
Some expect you to tell them everything about what you've been doing, why you left a role, what you'd ideally like in a role, your work status i.e. do you need a visa.... etc etc.
These are 'fishing trips.'
If they have a role they seek to fill they might reasonably be expected to have a job spec.
Often they want you to say how you would achieve a potential remit; beware, you might be writing the job spec. for them.
I'm not going to list on an open forum the Companies I feel are on-par with 'used car salesmen' or 'double glazing people.'
Remember, jobs are like houses... there are buyers and sellers and often there is no need for a middleman who gets in the way and takes a slice of the action.