system
A chat on subreddit /r/NoStupidQuestions
human
Other than it being disrespectful, no he doesn't owe anyone an explanation. An adult may come and go as they please if they pay rent. If not, they should play by house rules, but again he can leave for 3 days without a word if he felt inclined to do so.
gpt
“Just off out; I’ll be back for tea!”.

No explanation, but it does let everyone known where he’s gone (‘out’), when to start worrying about him and whether he wants tea or not.

Common courtesy.