Have you done much hiring in IT? If not, you'd be astounded by the sheer amount of crap that comes flying at you for every job you post.
You'll have literally one thousand resumes to sort through, and of those, roughly one thousand are terrible, poorly-written, undirected resumes from unqualified people. You have a few seconds at most to decide if a given resume is worth even reading, and you're in a headspace where you're pretty certain the answer is "no".
In that atmosphere, the chance of me looking at your undirected boilerplate resume with no cover letter and deciding that hey, this guy stands out, is exactly zero.
Try it yourself if you want. Better still, look at all the people who can't find a job in this industry, and the tactics they're using to market themselves. Chances are you'll discover a lot of them using the "send the same resume to every single job posting on monster.com" method that you recommend.
And they're going to stay unemployed until they change.