Yep, if you have to draw the Sun, you better draw it yellow. If you have to draw a cloudless day sky, you better draw it blue.
That doesn't apply to every single instance of those, but if the sky isn't the focus of your application, a realistic one is just a distraction.
> Yep, if you have to draw the Sun, you better draw it yellow.
This one always gets me in how dirty the sky must have been "back in the day" in order for people to see a yellow sun. I've never looked into what gas would be needed to make the sun look yellow, but it must have been hell to breathe.