It's possible this might vary by company or by recruiter.
We don't make much use of external recruiters for technical roles (there are a couple that we do use from time to time). We do talk to them about their candidates, and they have warned us off people they've spoken to who were rude or demanding.
We also have an in-house recruiter as part of our HR. In technology we don't often approach people directly (i.e., headhunt). I seem to recall we used it once for a leadership role a year or two back, but ended up hiring a referral instead. If you're demanding with our recruiter I may not even hear about it because they might reject you on my behalf (a decision that I will always support). But if you have been tricky to deal with, we'll certainly talk about it.
That doesn't mean we're completely inflexible either: we pick a time of mutual convenience to talk, but we are going to want to talk. Quite often people will want to talk to use to find out more about a role before they go into a formal selection process. Again, we schedule these at a time of mutual convenience. We often reschedule telephone and in-person interviews (not that we've been doing a whole lot of those for the past 15 months) at candidates request because life happens.
There seems to be some belief amongst a number of posters on this thread that the only or main reason we want to talk to you is so we can cut to a salary negotiation and hammer you down. That simply isn't true. Here are a couple of other important reasons we want to talk:
- We can learn a lot more about who someone is by talking to them than we ever can by email; the same goes in reverse. That call is as much about helping you figure out whether you want to proceed with your application as it is about us taking you forward.
- It's generally a lot quicker to deal with candidate questions on a phone call than it is in a potentially long email chain: I'd rather have a 10 minute call with someone than spend 30 minutes writing an email. This has benefits for both parties: both are usually busy. Time is often of the essence for both.
We often do not talk about salary at all in an initial conversation unless we're concerned that there's a significant mismatch in expectation: we don't want to waste anybody's time.
Again, let me reiterate the advice: don't be difficult. It doesn't matter whether you contacted them, or they contacted you: if you're really interested in the job, then be accommodating. This doesn't mean you can't come to some mutually convenient arrangement, but don't be a pain about it. If you're not interested then either ignore them (they won't take it personally, or even remember), or politely decline. You can even politely ask for more detail and politely decline if they're not forthcoming. That's fine, but there is no scenario in which it is beneficial for you to be difficult.
This advice holds true with every company I've worked for and every reputable recruiter I've worked with.
[This is not to say I've never lost my rag with a recruiter: I gave one a polite but firm telling off the other day because he kept phoning me to try to hawk candidates to me (yes, they can be as painful for hiring managers as for candidates). His line of thinking was that because he'd sent me an email in the morning saying he'd like to talk to me in the afternoon, my silence was a tacit approval for him to call me. It was probably the third time he'd called me when I was either in the middle of a meeting, or feverishly doing pre- or post- work between meetings, and I'd just had enough and pointed out to him that this was not OK. I still said please and thank you, and I did not shout or swear at him. I do get that pushy recruiters are annoying but this guy's behaviour represents only a tiny, tiny minority of my interaction with recruiters over the course of my career.]