If you're anything like us, then you have multiple accounts for multiple purposes. Maybe you have one for your work life and one for your personal life, and even another for another realm of your life. To account for this, Google has begun offering multiple sign-in capabilities, allowing users to sign in to multiple accounts from the same browser.
The feature appears to be rolling out to some users and not others (we have yet to see it), but Google assures users that it is "working hard to enable this feature for everyone".
I have a couple different Gmail addresses that I use for different purposes. Historically, Google Accounts – including Gmail accounts — have only let people access one account at a time per browser, so using both accounts has been a bit inconvenient. I’ve either had to sign out and sign back in, use a second browser for my second account, or use a Chrome incognito window. And I'm not alone; lots of people have asked us for a better way to use multiple accounts at once in the same browser.
Now, you can visit google.com/accounts and click the link next to "Multiple sign-in." After you sign into your first account, you can sign in with up to two additional accounts from the new accounts menu in the upper right hand corner of Gmail, then easily toggle back and forth between them. You can even open multiple Gmail tabs — one for each of your accounts.
using one password across multiple services isn't a security improvement.
I'm sorry, I don't understand - are you somehow forced to use it?
Its still different accounts and passwords, but you can sign in at the same time in more than one.