When a Girl is on disability and calls you to come over - you agree and spend some time with her - her "Card" gets labeled "Visited" and you cannot interact with her anymore that day.
What is the idea behind this? Or is this unintended?
This actually dates back to the original version of the game. I intended to prevent the awkwardness of going back and forth between your home and an immobile girl's three times in the same day. Working girls would only be available in one timeslot per day (as this was before the days of the week & days off work), so I added the 'Visited' system to limit visiting immobile girls to once per day as well.
I think you're right to question it as it is obsolete now, really. I might look at improving this in the polishing update I'm working on.