I've definitely seen people told there's nothing left for them to do, and their accounts and access immediately turned off. Why would they need access to system

I've definitely seen people told there's nothing left for them to do, and their accounts and access immediately turned off. Why would they need access to systems or the office if they have no tasks? Are you saying there's some kind of right they have as an employee to come in and work even if they are told not to and there are no tasks assigned to them?