it’s because the larger than stock rear tires are on a bigger rim with the required offset to get them to fit. There isn’t anymore room inboard. That usually requires certain sacrifices, and modifications ( tire rub/ damage, wheel lip rolling, beating the piss out of the inside wheel tub). Sticking a stock width wheel out farther than the mating surface will only succeed in you doing both of the things required to get a fat tire to fit when you didn’t need to. And it’ll have the same effect as a wing spoiler on your roof. ( insert the words “ bad idea” here).The car ( any car ) looks better with the tire inside the wheel tub.
If you just have to have a tire even with the wheel lip, buy a 10” wheel and a 295/315 tire.
Then you’ll know first hand why there are so many pictures of those cars with the tire sidewall even with the wheel lip.