[matheist]

I've also experienced this. My guess (I don't know for sure) is not so much "so you can't go behind their back and cut them out of a fee", but rather "get you to commit time to them so they have a chance of forming a personal connection".

I haven't had hardly any of them push back when I (extremely curtly) ask for more details. I usually say something like "company name / role description / location / comp? I don't have the time to take calls for every message at that level of detail when I'll probably end up not interested"

Usually they provide the details after that, though sometimes they try to drip it over multiple messages. That's why I think it's not about the fees.

Edit: I've never thought to ask them that directly! Maybe they'd be forthcoming about it.