Why do USCIS ask for passport renewal?

So both my parents have lived in the U. S. for quite a long time now. They have work authorization card and drivers license. However, every couple of months they need to visit the USCIS Office and every time they go the officers ask for them to renew their passport. It’s gotten to the point where they haven’t renewed their passport in years and my dad has to go do a face scan through an app every week and once a month, he has to go down in person again with another agent who does the face scan thing.

Both are really afraid of being sent back if they renew their passports. They have a fear that if they renewed their passports, the USCIS officer will buy a plane ticket and send them back to their country of origin. My mom is applying for a green card so I’m just saying her and my dad renewing their passports is just to confirm their identity’s and might make the application process easier. Is there another reason why USCIS officers ask for passport renewals?