If you really want the job, this is a bad idea. The form is there so that HR (who usually knows nothing about the technical details of the posted jobs) can match base requirements against what the hiring manager is looking for. If they get a match, they just forward the resume to the manager. Doing stuff like this on the form is likely going to result in them just moving on without looking at your application further. And it doesn't mean it's a bad place to work; the company and the manager might be great.
As a hiring manager, I am absolutely floored how many people do not actually have this information on their resumes. So while most people would assume a lot of redundancies between the form and a resume, I can assure you that many people do not have this information readily available on their resumes.
We all, deep down, understand the exploitative of the employer/employee relationship. They are setting the tone for the rest of your life doing bullshit work that doesn't matter at all.
If you ever get through to a person high enough to answer your question of: "why did you ask for my resume?"
...the honest answer is:
"There are two things that look at you, the candidate. For cost cutting reasons, we put your answers you fill in all these blanks into a computer which eliminates you if you don't match our basic criteria. We save money by never actually even knowing your name. If you pass the computer filter, your resume is needed because actual humans look at it. So thats why we ask for both."
There's actually an easy technical fix for this. All we would need is a common format for resumes that is machine readable, e.g. an XML schema that defines what fields should be in there. Then you just need a simple tool with a nice UI for inputting the info. So what are the chances of this happening? That's right, exactly zero.
I recently endured a job search. Applied to over 400 positions on Indeed alone. I stopped filling out the forms. Probably lost out on some job opportunities, but having to fill this shit out 30 times a day is not worth the effort.
Once when I was in High School, there was a test that had a fat block of instructions at the top. But buried in those instructions it said "You don't need to write any answers, just write your name and hand the instructor the test, and you will receive 100% credit." It was more a test to see if people would read and follow instructions than it was for knowledge. Needless to say, many people did not get 100% credit.
I can only guess that job applications are like that test in this regard.
I'm so glad I was able to establish a career and become well known in an industry before applying for positions was so demoralising and exhausting. I worry about what things will be like in another few years when my children enter the job market.
There’s a technical reason they do this that has been pointed out elsewhere but it has the added benefit of filtering out people who believe they are above the process. Most jobs have processes (safety processes, legal processes, etc.). You can avoid people who aren’t ready to accept they may be exceptional, but are applying for a position that does not require them to be.