Google integrates AdSense accounts with Gmail accounts.

On February 26th, when you log into Google AdSense, if you previously used a non-Gmail account, you will see the prompt interface mentioned above. It is recommended that you change your Google AdSense login account to a Gmail account. After switching to a Gmail account, your AdSense information will remain unchanged; you will just need to remember your Gmail account and password going forward. This is indeed much more convenient. It's a feature I've been hoping for, and I didn't expect Google to actually implement it. I think this might be a prelude to Google's integration of its various platforms.