"I haven't even figured out why Lee includes them with their dies."
I have; they scoop up powder for reloading. It helps to follow directions tho.
If used well dippers are as consistant as any other volume dispensing tool. They're fixed so obviously no one is going to adjust a dipper to obtain a specific weighted charge, that requires an adjustable dispensing device. How desireable being able to pick out a specific charge weight and get to it generally requires dropping low charges on a scale and trickling up to weight anyway; dippers will do that as well as vastly more expensive cast iron measures.
Contrary to popular assumption, how much charge variation before it shows on targets will vary by several factors but few charges demand consistancy to +/- zero grains. A well developed and carefully assembled load will tolerate a charge range of several tenths variation without any visible effect on target - no commercial ammo is weighted and some of it shoots phenomenally well.