In my experience it's more psychological. Just knowing a trade may happen any hour doesn't let one fully relax as opposed to say, long-term investment when you care less even about various flash crashes etc.
From another viewpoint, if there are enough trades every day, there's no biggie to miss a day or a couple of weeks simply if you want so, especially if it happens around holidays or late August.![]()
That depends on the instrument, how much it moves (duration and extent), and what one wants. If one is concerned about "enough trades every day", then he's daytrading again. Or he can trade a daily chart. Or a 2d chart. Or 3d. Trader's choice.