Simple: You get all of your images close to the meridian! Huh? Read on...
Most astro-photographers don't image multiple targets in a night. Why not? Tradition. They haven't had the capability, and haven't thought about the big advantage. It usually takes many hours to acquire enough raw images to make up a "good" astro-photo. Of course, taking each image one at a time is labor intensive, requiring many mouse clicks and staying up all night clicking buttons to take images, save them, change filters, refocus, etc. So of course tools like the sequencers in MaxIm DL and CCD Autopilot are attractive. But -- these tools automate imaging of a single target.
Multiple-target automation is good for astro-photography because you can image during the best seeing! Rather than image one target all night, including times when the target is low and the seeing is bad, you can image several targets while they are high. Then you just repeat this over several nights. The result is that all of your images are taken through a minimum of atmospheric turbulence. But what about meridian flipping?
ACP is the first automation tool to handle meridian flipping automatically. Others have copied this feature, but ACP users have enjoyed this capability since 2002. And since it supports auto-calibration and auto-stacking while imaging, of course it knows that images on the west side need to be rolled over (after being calibrated of course!). We're always ahead of the competition.
Anyway, let's say you have 6 hours of good darkness. Obviously, it would be better to take 2 hours each of three targets over three nights, while each is within an hour of the meridian. Your images will be superior, allowing you to blow your fellow astro-photographers out of the water with quality. Don't believe the people who say that the color components can be acquired through high air-mass without loss of quality. Yes, you will be binning them 2:1 typically, but the typical astro-photography setup runs at 1 arc-second per pixel or less, so even the color components require 2 arc-seconds per pixel for best quality. Can you say that your skies support 2 arc-seconds per pixel more than an hour from the meridian?
There are many reasons! For more information, including videos, technical info, and general overview, see the ACP Home Page.