Apple could never understand that there can be more than user on a computer.
Hand-me-downs, temporary laptops in corporate settings, any laptop (or iPad, or iPhone) with more than one user/owner will inevitably run into this issue: a few (or not a few) apps installed by the previous owner persist. The account has long been wiped, and a new owner has moved in.
And yet, if you try to update anything (including Apple's own free apps they distribute with every computer and account), you'll need to provide the previous owner's credentials.
The best thing about it? There's no way to remove the previous owner, see the full list of apps they downloaded and transfer ownership or quickly delete them. They show up as if you owned them and will ask for a password on any attempt to update.