Unlocked and unattended computers are a security risk. They give someone who has bad intentions an opportunity to steal personal data or even breach a computer. It is an industry best practice to automatically lock a device after some proscribed period of inactivity. The state of the locked device is preserved, and individuals simply need to sign back in to resume use. Many, but not all, university computers currently have the screen lock set to some nominal time.
A 15-minute screen lock policy for personal workstations has been tentatively scheduled for February 29th. Classroom computers will be excluded from this change.