If you are not the first owner of your Mac, you might get prompts asking for the original owner's Apple ID for updates – even after you've removed all of their identifying information.
That’s because Apple encodes the buyer of OS X and the apps into their respective installations. Even though the OS X is free and some apps are native and come installed with a new Mac, they are still linked with the Apple ID used at the time of the first download.
How to fix this
This is extremely easy to fix. When you get prompted to enter the old user’s login identity, enter your credentials instead of the old user's. No, this is not a joke! However, for paid software, you’ll have to use the buyer’s Apple ID and password whenever you want to update the application.