There’s a game online that lets you feel the edges of subitizing, called 12Many. A number of stars flash up at you, for a fraction of a second, and you have to say how many. It gets progressively more difficult.
As the number increases, you find yourself dividing the stars into groups to count them, to try and fit the counting—sorry, fit the subitizing in, in the allotted time.
And aside from games, is this important?