called that becuase the race cars would driver over open pit lane to stop above his crew that could then quickly get work completed without using a jack to get up under the car. Remember, cars didn't even have oil filters until, what, the 1920's? The model t didn't have an oil filter and had to have the oil changed every 300-400 miles.
learned about this (should have been intuitive) and photos from http://thechicaneblog.com/2010/08/10/in-the-pits-at-the-vanderbilt-cup/