So my wife is in HR, so let me explain why they use these kinds of systems...
First, for any particular job opening managers are putting pressure on to get the ad in the paper, get the notice up on every job posting board there is, get word out to employees, headhunters, etc. They want their position(s) filled as soon as possible, many times they feel like if they don't get the job filled right away some bean counter might realize that the job isn't really necessary and lots of money can be saved by eliminating the position.
Now with all of those postings someone has to create the actual ad and job description. This is pretty tough since managers will tend to ask for specifics (must know how to use the 1980 version of drill press 123), but this has to be translated into something that is a little more open to receiving viable candidates. There's also the challenge of getting all of the requirements from the managers so the posting is complete.
Then the fun begins. Headhunters want to provide 'screened' candidates (which end up being a result of a query on some database they have that kicks back a list of folks that may or may not have all of the skills necessary). There's also a lot of cruft and spam that come in for the job posting (lots of job bots out there), and there's also people who are not really qualified for the job applying anyway cuz they're looking to make that next big career move. And with the glut of unemployed out there, you get folks who are out of the area, folks who are overqualified, underqualified, etc. who all just need a job to keep their house, car, kids, dignity, whatever...
Many of these sites that are used are not really picked or coded by HR in any way, they're generic sites (perhaps themed, but generic none the less) like zip recruiter (POS, if you ask me). These sites love applicants and resumes etc., but they also employ some sort of "qualified applicant" filter so that all applicants don't ever get to HR. And no, HR does not usually pick these kinds of sites, they'll get picked by business folks who are looking to save money in the organization and get convinced that zip recruiter will help them do that.
Another thing companies are using are personality tests. They too are sold to executives as ways to automatically filter out 'incompatible' people. In some cases they may work, but in reality they can typically be gamed to get you through. Surprisingly though, many folks don't know they can be gamed and answer them honestly; unfortunately for them, the execs tweak the test so much that only supermen get through (i.e. like a salesman who can sell ice cubes to eskimos kind of perfect candidates). Many times these filters end up being over-aggressive and end up blocking what may otherwise be good potential candidates had they known how to game the tests.
As far as the uploading resume goes, well those end up going to the hiring manager (because they want resumes, not forms or reports). The forms, however, are necessary for all of the computer filters, etc. to weed out unqualified applicants. They have no real HR function outside of that (although it is easier to work off of reports of candidates).
Finally, just as it is in IT, if you want to screw something up really bad in HR just get the executives involved. They're the ones that mess things up over there just as much as they do in IT...