Oh, they are full grown adults. During the week, they are grinding at work. Sometimes they just want to come home and reset with their own family (wife, kids, games, catch up on shows, whatever). Not sure what their commute or work is like, but I can definitely see dipping out on random family events early or just not going out completely. Especially during working days.

I think you just need to plan it better. Maybe schedule family dinner and events on the weekends.