HR Types, is this necessary?

I do seasonal work for a large company. I keep my same employee # year after year (so they keep info on me in the system); however, every year I have to fill out the ‘full’ application, including going thru the I-9 employment verification process.
Once I’m in their system & have been verified do I really need to do this again as I am rehired less than one year after being terminated/separated? Surely a company this large rehires people all the time, especially seasonal ones & has the ability to keep “I-9 verified” as a check box in their system.
I could see maybe not wanting to do this for a visaed employee but does citizenship status change? Presumably if I continue to live here I would remain a citizen as I’d assume if I wanted to become a citizen of Country X, I’d also want to live there & not be an ex-pat staying where I was. Does this happen, changing citizenship but remaining in original country?

(This was the first & only time I used my passport this year.)