The incremental download enables people who have a slow internet connection to finally download games and apps from the Google Play Store instead of waiting hours or days until they can get what they want.
It doesn't matter if you are using Wifi, 3G, or even 4G LTE connection; there is always a quiet spot on the way that will prevent you from obtaining MOD APK.
Most people don't know this but still, keep complaining about how long it takes to get what they want. Well, if your internet speed is below average, I suggest you use the incremental download all the time since it reduces your waiting time by 50% or even more!