I believe this is an issue related to the lack of a proper day-night cycle, and related consequences.
I concur with this. I think it was Larian's way of making sure you are technically getting 1 long rest a day. Since using it "ends the day" you are always camping at night. So even though a player can spam this as much as they want, apparently in game logic is they lounged around for most of the day after having one fight and retired to camp for the evening.
