We are extra vigilant with putting heavy security measures on our devices for privacy sake but its actually not such a good idea.
If your device is lost or stolen its very difficult to trace the owner and thus leaving the thief to flash the phone deleting everything on it and sealing ones fate of not ever finding their phone again.
A way to solve this is through app lockers which from their name are applications that allow you to put some security on the applications you require some privacy.