There is an option in Optimisation job that remove unused space from database file (shrink database when it grows beyond and amount of free space to remain after shrink).
I heard that this option is not really recommended to apply. Is this correct? Any reason? In fact it's only running once a week.
Yes...It's better not to excercise that option unless you are deleting heavy chunk of data from the database. There will increased IO and fragmentation after you do it.