For me, it’s like “why not”. I store basically every documents in my computer, which is connected to iCloud.
I have my citizenship (basically a birth certificate for immigrants) scanned and uploaded to iCloud, just in case my house burns down or something. Along with passport (which I also scanned and uploaded on iCloud), it’s my proof that I’m a citizen. As a person of color, it will save me from a ton of trouble by having some sort of proof of citizenship.