Liability can be shared and a tenant may greatly prefer going after an ex. landlord vs. some random person.
Granted, this does not apply in your case, but Chicago does have mixed use Residential/Commercial leases which is covered.
Now suppose a tenant goes back to retrieve their property the day after there lease ends. Which under some situations they are allowed to do. Key works, the enter building...
IANAL, but would suggest this is a situation the owner would like to avoid.