Why 3rd party company doing my background check is feeling me to upload all my w-2s from every year I’ve been employed?

I’ve been working since age 16 and for the first time the company that is performing my background check to my new potential employer is asking me to upload all my w-2s. I’m curious as to why they are requiring this. Never had to do this for the 7 different employers I’ve had in my life and frankly I don’t think I even have those forms from over 10 years ago. Any idea as to why and how this all works?

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