Casinos only take a keen interest because they fear fines, nothing more. They care because they have to.
They'd let players gamble away the hours merrily all day every day & twice on Sundays, and not care if you blew the mortgage payment that week, and that's the facts.
And yet even then they can't find the common practices among gamblers, because it's fairly unique in that sense. The entire experience is different for everyone, and with mobile gaming thrown into the equation, pretty much omnipresent.
Though if looking at gambling as a whole, I'd imagine it's busiest 'evening onwards', leading into the early hours. Clearly at b & m casinos, but online too? Not to mention a great time to get some peace and quiet and immerse oneself in the games!
The notion that casinos themselves view those as unsociable hours is absurd of course, and goes against common sense. I'd wager that spinning furiously during work/ commuting/ day task hours is by far the more unconventional. But I won't be holding my breath for casinos to start prohibiting 'sociable' players during the day and rationing their play time