In their pre-rebirth life, the driving motive of all of life was acceptance in the broader community (see on 1 Peter 1:14 about the passions of your former ignorance
). In a post-rebirth life, the driving motive is conforming to God, that is, being holy. Clearly, that cannot refer to a portion only of one’s daily existence, but of necessity it must characterize “all your conduct.”
15 but as he who called you is holy, you also be holy in all your conduct,