Why do recruiters often want a phone call before sending a job description?

I am often contacted by recruiters on LinkedIn, asking me if I would be interested in applying for a job they're recruiting for. While I am happy in my current role, and not actively looking for a move, sometimes these roles sound interesting from the descriptions given, and I ask to see the full job description in order to decide whether I would be interested in discussing further and potentially applying.

In the past, even when not actively looking for a new job, I have been happy to take these calls to discuss the job (basically just have the recruiter tell me over the phone what is in the job description, in more of a 'sales pitch' type way), as what they had mentioned in their message on LinkedIn had piqued my interest enough to make me think I might consider it.

However, I often found that I got more about what the job might entail from reading the job description than from talking to the recruiter, and so started asking recruiters to send me the full job descriptions when they contacted me on LinkedIn before agreeing to a phone call with them - if there was anything in the job description that was unclear, or anything I wanted to ask more about, that was the opportunity to do it. It also allowed me to screen out jobs which the recruiter may have tried to 'match' to my profile in their description, but which were actually not that well suited to me/ weren't something I was particularly interested in.

Over the last couple of years or so, I've found that recruiters now tend to be unwilling to send over a job description for a role they're recruiting for, without first having a phone call, which makes me far less inclined to agree to a call with them, as I feel a call would only be worthwhile when I know enough about the job to know I'm interested in discussing it further.

Why is this? Is there some legal requirement for them to speak to a potential candidate over the phone before sending them the job description? Are they worried that if they send the job description, and/or name of the company the job is with, I might try to apply to it myself, without their representation? Is this unique to the UK, or is the same practice followed in other countries?

The job of a recruiter is to take you (the product), evaluate whether you're a good fit for the role, and then to try and sell you to the company (their client).

Before they do that, most recruiters will want to speak to you to verify that you're a real person, and that you're a suitable candidate and one that they want to put forward. A big part of their role is to perform that initial screening of candidates - if the company just wanted to stick a job advert online then they wouldn't bother using a recruiter.

It also allowed me to screen out jobs which the recruiter may have tried to 'match' to my profile in their description, but which were actually not that well suited to me/ weren't something I was particularly interested in.
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I feel a call would only be worthwhile when I know enough about the job to know I'm interested in discussing it further.

That's fully understandable from your perspective, but from the recruiters side they also need to decide whether you're a worthwhile candidate for them to be recommending. And especially now that so many people's CVs all look the same because they all generated them with the same LLMs, many recruiters want to do that via a call.

It also provides them a chance to learn more about you than they would just reading your CV/LinkedIn, and whether you might be a good fit for other roles. Or whether your CV looks great, but after speaking to you they realise you're not a good fit. And it also helps them keep the communication flowing through them, because if you cut them out and go around them then they might not get paid.

Remember that the recruiter isn't working for you, and they don't care about you or your interests. They're not trying to find you a good job - they're trying to find and recommend good quality candidates to the company that's paying them. So they do what makes that easier for them, not what's convenient for you.

Next time you speak to one, pay close attention to the questions that they're asking on the call, and that'll give you a clearer idea of why they wanted a call and what they're trying to get out of it.