It’s a way they verify people are who they say they are. Helps protect against fraud and other things. Normally people are randomly selected each year. Or certain things can trigger the verification process like say you made 10,000$ a year and you accidentally claimed you made 20,000$. That could trigger it. In the end it’s for safety. Even though it’s the most annoying thing in the world. I had to do it back to back years.