The servers storing this information have been hacked in the past and it will happen again in the future. The fewer places your ID lives, the lower the risk of it leaking.
Even if you don’t view the data as sensitive, it still associates a person with a website. Depending on the site, that can have negative ramifications in a person’s life. This is especially true when certain websites get associated with various political leaning and when the data leaks, the people who happened to be registered (for whatever their reason) get attacked.
My company has rules against retaliation. Good luck proving that’s the reason you didn’t get promoted, or were left off of a project. People get left off projects and don’t get promoted all the time. Keeping your job because the company is legally obligated to sounds like an uncomfortable working environment.