Cover letters matter to some people, which is why you should do it if it's a job you really want. I wrote one for the last two or three jobs I've gotten.
I think it is an extra hurdle to weed people out. It separates those who do blind resume dumps from those who actually sat back for a second and really considered the reasons they want the particular job.
Yep. When I'm looking at applicants and someone doesn't write a cover letter while everyone else does, I assume the person who doesn't write the cover letter doesn't really want the job. It really doesn't require that much effort to write one if you've done it before.
Agree. I tried applying for a handful of internal positions within recent weeks (resume/profile only) - nothing. Then I sent a cover letter-like email for each job (but less paragraphy and boilerplatey) - something like 70% response rate within 2 days. That's all the evidence I need that they are worthwhile. I think software is one industry where the value is questionable given that sites like github and stackoverflow provide more meaningful predictors of competency than even resumes in many cases, but I think cover letters are a really, really good indcator of how much applicants care, which has to correlate to the odds of the applicant accepting the job (i.e., not wasting the hiring team's time) if offered.
Also...I generally don't review cover letters of interviewees (interviews/resumes only), but I am genuinely shocked at how awful some of the follow-up ("thanks for ur time!", I never learned subject-verb agreement, etc.) emails are. I can only imagine how bad their cover letters must have been - would have been automatically no-piled if I'd been the one screening them. Side note: I generally assume that I overestimated someone's IQ by at least 10 points and that they are really desperate if they send a trite thank-you e-mail to my engineering team (through HR) after the interview. For eff's sake.
Recent revelation for me: "objective" statements are usually absurd and have no place in most resumes (unless your intentions are truly unclear). Ditching those 3-4 lines of nothingness allowed me to condense the old 'sume to one page and make pretty much every character breathtakingly impressive. I didn't realize that objectives have become passe. How embarrassing!