It was part of the account creation process to verify your identity. You had to send in a government issue id and proof of address. I believe I sent in a copy

It was part of the account creation process to verify your identity. You had to send in a government issue id and proof of address. I believe I sent in a copy of my drivers license and a cable bill but passport was also an option. I wouldn't be surprised if they have access to all the data that was collected for KYC purposes.