Many iPhone users want to lock chat apps and photos because real privacy problems often happen after the phone is unlocked. Someone borrows the phone for one task, then another app is only a tap away.
Chats, photos, files, notes, email, and work tools are common candidates for app-level protection. They do not need to be locked all day, but they should have a boundary during shared-use moments.
The most practical setup is to create groups by situation: lending the phone, child use, work focus, or private media. Lock the group that does not fit the moment.
iPhone Locker is designed for this style of app locking, helping users protect specific iPhone entries without changing how they use the rest of the device.