Why do people buy normally expensive breeds from shelters?

I'm probably low IQ but I don't get it. The reason why I'm looking here is because I don't want to give my money to a mill. I know you can normally find or rescue a breed but it's extremely hard to do that. Would y'all rather get a mutt because there's so many of them that are already dying/struggling in shelters. I don't have a preference at all in dogs, I'd be happy with any kind of dog but I'm sure you're not gonna find a Great Dane in your local shelters normally. Do people just not care as long as they "rescue" a dog? No disrespect to anyone