I think in these cases it's simply a numbers game. I mean it's just spam but slightly more targeted. It's the same rules, though. The more of these they send out, the more likely that _someone_ is going to respond. And I don't think these types of recruiters care much about whether you are a good candidate for the position in question. They just want their commission.

And maybe you respond and tell them to remove you from whatever list they have you on because they clearly haven't done their research on you. Or maybe you figure "one phone call hurt just to see", and you chat with them. Well now you're in their database, only slightly more targeted for the next time around.

They don't want to tell you about the position details because they don't want you bypassing them and applying directly to the position yourself. They don't get paid that way.

It's no different than salespeople. They span the spectrum. Some salespeople are slimeballs who will tell you anything to make a sale. Some are actually good and will make sure you get a quality product and are happy. The vast majority are somewhere in between. It's just like any other type of business, frankly. These guys, though, are just playing a numbers game. They are basically the telemarketers of the recruiting business business. Or the shady car salesman. Or whatever parallel you prefer.

There ARE good recruiters. Particularly those that specialize in more higher-level positions. But unfortunately these crappy recruiters tend to drown everyone out, so it becomes hard to separate the good from the bad.