They are not. They may act like it, but they represent the company they work for, and ultimately their own interests. Some recruiters have enough integrity to be honest with you, but some don't.
If you want to know who you can trust, you need to know what motivates them. You can trust they will act in those interests. You can trust them to act in your interest when your interests align.
Agreed, yes. Recruiters generally do want to place you and collect their fee, but few would have any qualms placing you at a terrible firm that pays well (=good fee) and keeps you doing the same shit for a year before going under, rather than a place that pays less but has great corporate culture and an engaging job with growth potential.
They are not. They may act like it, but they represent the company they work for, and ultimately their own interests. Some recruiters have enough integrity to be honest with you, but some don't.
If you want to know who you can trust, you need to know what motivates them. You can trust they will act in those interests. You can trust them to act in your interest when your interests align.