The problem with cover letters is false positive (people who did not write the letter themselves, or who did it to a much higher standard than their usual). But then, that’s what interviews are for.
I did hire a couple of people with either a subpar CV (some good people sometimes end up in dead ends or difficult situations), or cover letter (not everyone is a great writer), or reference (your issues with your former boss are not always your fault), or interview (you can have a bad day), so I would not rely on a single factor. But a combination of 2 dodgy elements is an automatic rejection. Each one tends to surface different aspects.
Nobody is spending 10 minutes writing a cover letter.
Companies that are getting hundreds to thousands of applications are not reading every cover letter.
Show me who you are and I’ll show you who I am, and if we like eachother, then let’s try to get together and see what we could build together. if the entire interview process is a series of hoops that you dictate I jump through to even have a chance with you, then why should I expect my future with you to be any different? I don’t want that.
I don’t want to write a carefully crafted letter pretending that I want anything other than respect and money and a chance to do work on interesting from a potential employer. I just want to write code. The rest of it is extensive shit testing in my book and I have no patience for that. I don’t put up with that kind of treatment from anyone else - what makes you think dangling money in front of me would change my mind about that?
CV is nice except that most people have a list of "Senior Software Engineer at XYZ" and that's it. Doesn't tell me anything, so again, if that's what you're going with, I'm going to prefer the person who took the time to actually talk about their related experience and interests. LinkedIn is nice but same problem as with CVs.
Seems like you think everyone has perfect detailed CV and LinkedIn profiles... Nope. It's mostly crap that says nothing. If your CV/LinkedIn can take the role of the cover letter then sure, no problem, but I don't see that often.
Not sure how the recruiter's notes about your nice friendly outgoing personality and good English level would help me understand your experience and interests related to the job, but yeah sure lol.
No crappy ATS at our company, BTW. Applications go to the inbox and are handled by real people.