I hate queries.
You hate queries.
All writers hate queries.
If you don't, then I demand you turn in your writer card right now because you're an imposter.
However, queries are a necessary maybe not quite "evil", but close. I think most of us have heard the reasons they're needed:
*For writers, they're a foot in the door with agents.
*For agents, they're a first taste of a writer's skill and voice, as well as an introduction to the story. (They're also a 1st line of defense against those who simply can't be bothered to follow directions and/or learn their craft.)
I've also found that queries can be a valuable tool when starting a new story. (I know... I'm as shocked as you are.)
When starting a new story, after you get the basics down, try and write a query for it. Seriously. Do it right now. (No, I don't care that you don't have a new project in the works, I said move it! :-P )
It may sound counter-intuitive, but starting with the query can not only help you map out the major plot and main characters of your new project, but it can also help you dodge plot problems before they wriggle their way into your MS and have to be surgically removed. It spotlights those nasty cliches that you can't pick up on when they look shiny and new in your head.
And the single biggest advantage of the query before writing method? You find out in advance if you know your story.
If you can't explain it concisely from the beginning - before all the juicy details are added - then you most likely don't have a handle on the essence of the story yet. You are, in essence, trying to build a house without a foundation, and that's never a good idea. (Neither is using "essence" twice in two sentences, but it's a repetitive day... just go look at Nathan Bransford's blog post.)