I look at a lot of job applications submitted via the Web and I am consistently surprised by the number of applications that I see that don’t include cover letters. The thing is, I also know a lot of people who never read cover letters when they’re processing job applications. When you skip the cover letter, you take your chances.

Here are some of the things I wonder about when I see an application that doesn’t include a personalized cover letter:

Are you applying to so many jobs that you can’t be bothered to write cover letters? We want people who want to work with us specifically. Giving me the idea that you want “a job” rather than this job does not put you on good footing.

If your résumé seems oddly suited to the role, I usually assume that you didn’t actually read the job description. You can clear that sort of thing up in the cover letter.

If your résumé is not really well written, I assume that you didn’t include a cover letter because you’re not good at communicating in writing. I put a high value on the ability to communicate in writing.

The final thing I may assume is that you just didn’t care enough to bother with the cover letter. You were provided with the opportunity to do a little extra work on the application and you skipped it. In my mind, this reflects poorly on an applicant.

When I look at an application, I look for the cover letter first. What I’m looking for is an explanation of why you’re interested in the job and how your skills map to the requirements in the job description. A paragraph or two will do. This is also your opportunity to convey your passion about the company, the work, or both.

Leaving out the cover letter requires me to use my imagination when it comes to mapping your experience to the job requirements. If that’s a no brainer, you may be able to get by with skipping it, although I don’t recommend it. If I’m looking for someone to do PHP development on a high traffic Web site and your previous job was at Yahoo doing PHP development on a high traffic Web site, you may not need a cover letter. I can figure that out. If your previous job was doing Ruby on Rails development on an academic project, more imagination is required on my part. Why leave it up to my imagination?

The cover letter is one of the only opportunities you’ll get to provide information to help make the hiring decision. Unless you customize your résumé for each job, it’s the only shot you get to tell me exactly what you want about yourself. I don’t particularly like to phone screen people. Before I schedule a phone screen, I’m going to go on the Web and look at your LinkedIn Profile if I can find it, your GitHub account if you have one, and anything else that comes up in the first few pages of a Google search.

One other benefit of writing a cover letter is that it gives you the opportunity to do some sales, by way of explaining where you are in your job search. Let’s say that your résumé is an obvious perfect fit for the job requirements. If you’re already interviewing for jobs, including that fact will likely get your résumé handled with more urgency. Indicating that you’re happy with your job but you are really interested in this job in particular can be flattering as well. This is not an opportunity the job seeker should pass on. I write this as someone who’s reviewing résumés because I appreciate it when people are thoughtful about what they’re doing.