Car buying/leasing is as much emotion as it is economics. You'll have people that base their choice more on one than the other, and plenty of people who balance out their emotional desires in a car with the practical economic demands on their budget.
From a pure economic perspective, I understand leasing to be the least cost effective in the long run. You'll likely spend less money on the car payments, and have to provide less (or nothing) down, but you'll have a car payment that doesn't end. If you buy a new car with a five year loan you'll have something of value (you hope!) when that five years is over. After five years of leasing you're on your second car, but you don't "own" anything when you decide to stop. Leasing does, however, offer some peace of mind when it comes to "unexpected" expenses. Most of anything that could go wrong with the car would be under warranty, and the only maintenance you might have to pay for would be wear and tear related.
All of that said, if you're the kind of person that buys a new car every year, then leasing is exactly what you should be doing. You'll pay significantly less by leasing then you would be constantly buying a new car and trading it in. But this comes down to the emotional part of car buying. You may not NEED a new car every three years, but you might WANT a new car every three years. And if you do, then leasing gives you just what you want and saves you money at the same time!