You'll typically see this on the weekends and it's because it's not been implemented (I don't think there are even any interactions with them during the weekend).
Yep. There's very, very little weekend content overall other than the 2 date events with Christine (and her sister Caroline of course), and even that is just for the Saturday. Sunday might as well not exist for all the constructive uses a player can find for it - can't work at bookshop to earn any cash, can't interact with housemates other than bathroom scenes in the early morning and the possibility to watch TV with one of them at 11pm. Lots of other scenes are unavailable too at the weekends as most girls only have a Mon-Fri routine.
I get that it will change, and that far, far more events are planned, but it really does feel very limited at the weekends, especially in the time before unlocking Christine's dates (with and without her sister). Almost as frustrating as the unfinished shower scene with Christine. We are 2 years into dev (and more given it was in development for an unknown amount of time before the first version was released), and for the weekends to still have pretty much an empty map and empty events every week is... Disappointing.
I'd like to see at the very least some way to grind money at the weekends for the players who'd rather do something else during the week and not have to cheat the money. Another wish-item would be the ability to use the phone to proactively do a few simple set events to grind friendship or affection with the various girls.
However, this is wishful thinking from someone who doesn't know what events the devs plan to fill those timeslots with already, or how much production time is needed for each or any of those events. The date with Christine and Caroline on a Saturday evening is a pretty big event, with a lot of renders and animations. Adding those kind of events is a big task, and takes time.