Laptops, smartphones or tablets are never left unattended
Automatic locking after a predetermined period of inactivity means that a user does not need to worry about leaving their device open to be accessed, because the device locks itself and is protected by a pin code (or other 1FA system).
A possible solution is to encrypt the work stations and to make it compulsory for them to be switched off outside office hours.
Always lock work stations (CTRL + ALT + DEL or Windows Key + L) when absent. Also secure laptops with a laptop lock and a key to prevent theft.