[throwway120385]

Another fun fact is that it was impossible to deduce from any of Ben Franklin's experiments what material was transferred and what material remained in place to give rise to "charge" as we think of it. So he picked a convention that we've continued to use even after we learned that his negative charges were the material that gets transferred by friction.

[SAI_Peregrinus]

On the plus side, in electroplating the positive ions are what actually moves. So in the experiments where you can visually see something move from one terminal to the other the conventional current direction is obviously correct.