Because it’s not. You have a lying dealership if they say that. What they are really doing is two things.
1) I want to see if you’re a bum and can afford it or I’m wasting my time.
2) if you’re not a bum I want to see how high your credit is so I can dig the knife in a little deeper.
That’s 100% why they do it and also why I tell them to buzz off.