I don't haggle. At all. I've sold a startup before for 7 figures. You know how I closed deals with Fortune 500 companies when we were selling our product? "Here's the price. Please feel free to shop elsewhere if you're not interested." Same with selling the shop. "Here's the price (based on our fundamentals). If you don't want to buy it, cool, someone else will. Or it can keep printing us cash."
Not everyone does such things, and I'm sure among those that do, you'll find many who don't care to waste hours with used car slimesmen to save a few pennies.
Note that it's not "can't", but "don't find it worthwhile". I might pour my heart into a big acquisition while simply walking away at the first sign of hassle when trying to save $500 on a car.
Haggling is overrated.