This is to give the player the illusion of an actual everyday life. You also have to eat and sleep in the game (otherwise you risk a debuff), occasionally farm certain materials that you need for something, and last but not least, build up the A and C of the respective Li. And it all works and is well thought out, you can really sit in front of the computer for hours and not even notice how time flies. An contrast to other games where you get really bored and grind/farm to death. Then there are the alternative routes, which also distinguish it from typical sandbox games.
These well thought-out and interlocking features, if you get involved with them, give you the feeling of really being part of the game world and thus convey a pleasant atmosphere. I think that is what makes the game successful and sets it apart from the competition.