Why does the play store require multiple account login to display my apps in the Google play store I recently changed my 2nd gmail account password. 

When I open the play store to check my apps it gave an error:


Authentication required. You need to sign in to your account. (click image for larger variant)

Whereas I have already logged in my first Google account  then why does it require the second account to be logged in when I haven't used this account any time for any Android apps till date.
Pretty easy to answer – let me use an example:

I add your Google account as my secondary. Now I log in with my primary. Would you be happy if I wouldn't have to authenticate for the secondary now? That would enable me to do all kind of stuff "on behalf of you".

So, putting it in short terms: Security concerns. Whether you have logged in with the second account from any apps or not doesn't matter – that account holds personal data, which must be protected.