Why are some variables in my data cart preselected?

Why are some variables in my data cart preselected?

Certain variables appear in your data cart even if you did not select them, and they are not included in the constantly updated count of variables in your data cart. These variable are automatically selected because we think they are important for users. Unless you are absolutely certain you will not need one of these variables, we recommend that you not remove them from your data cart.