Grain bill weight, grain potential, strike volume, and end of mash SG can be used to
calculate your conversion efficiency.
Grain bill weight, grain potential, pre-boil volume, and pre-boil SG can be used to calculate your mash efficiency.
Grain bill weight, grain potential, post-boil volume, and post-boil SG can also be used to calculate your mash efficiency.
Calculating pre- and post-boil mash efficiency is a good way to check the accuracy of your measurements. If the two don't match, it means that you have excessive measurement errors.
Volume changes ~4% between room temp and boiling. Not knowing the temp at which you measured volume can mean you start out with up to 4% error in your calculations, even before you take other measurement inaccuracies into account.
Once you know your conversion efficiency and your mash efficiency, you can calculate your lauter efficiency (lauter eff = mash eff / conversion eff.) If you have low mash efficiency, you need to know if it's because of low conversion or poor lauter technique, as the fixes are different for the two cases.
If you don't care how your process is performing, then you don't have to worry about collecting data. But, HBT is full of threads about "why is my efficiency low?", "why is my OG low?", etc. These questions cannot be accurately answered without the necessary data.
Brew on