We don't have a 'digging patch' but thats because a) we have a cat who would use it as a poop patch, and b) we're renting a 'new' house in a new estate with no established garden, just grass, so unless we landscaped the backyard for them, a dirt patch would look a bit out of place come inspections/moving out. So if we didn't have a cat who would defoul it and were in a more established place, then yes she'd probably dig in actual dirt more often.

BUT, she does play in the grass, and some patches of dirt in the grass (after its been poo checked LOL!) and soggy muddy wet grass LOL. She's wrecked some pants and shirts, that are now her outside clothes hahahahaha. She does have fun, although it all stops when she gets a bit precious if theres grass on her face or in her hair