You can still buy an expensive car if you can afford it at the time, but being able to afford it at the time should include putting enough down to be ahead of the depreciation curve. My GTO was pretty expensive since I bought it with 1640 miles, but I put enough down that if at any point while paying off the loan something happened and it was no longer in my budget I could easily sell it cheap and still pay off the loan.
If I couldn’t have put that much down I wouldn’t have considered myself able to afford it. Unfortunately a lot of people don’t think that way. They say that right now, today, they can handle a $400+ a month car payment and that means they can afford it. They don’t think about where they’ll be in 3 or 4 years when they’re still stuck making that $400+ a month payment, or what happens if they have a life changing event like an accident, layoff, kid etc.