Often I think all these (cover letters are not the only artefact) are just postural items to see who's gonna make the effort no matter what use it has. A kind of faith leap.
I would do it for one or two companies. If you can be hired by the first company of your choice, you don't really need it.
What about providing a proper job description? Without it your company is a "maybe", till I talk to an engineer who can describe the job properly. Would it make sense to write a cover letter after that?!
