Because Leno is not in the business of buying and flipping. He has a huge collection that he enjoys. Carini is a car restorer AND a salesman. He can afford to be a pompous ***, and I bet he doesn't lose sleep about it. Hey, more power to him.
BTW, if you've ever had the occasion to visit a high-dollar car operation in your town like Carini has, I'd bet dollars to donuts that the proprietor of that establishment is probably as arrogant. There are at least four here in the OKC area that I can name that fit the bill.
I find Carini very interesting to watch. I learn something new every day about old cars from that show. The guy has been around cars his whole life and can actually turn a wrench, paint a car, and tune an engine. Lots of others like him into those high-end cars don't know a box wrench from potato salad.