Why do people have a blank sprite in their projects? I know griffpatch and others do this.

Scratch loads the code for the selected sprite and deloads others. When you have a blank sprite and you try to enter the editor, the waiting time is less because the scratch editor only has to load all assets and not the giant amount of code in the first sprite.

Well, it can be for many reasons! I used it as a reset for all my variables but then I used the background but it can be a future feature, an unused sprite, or they just forgot to delete it! The only way to know is to ask!

People like griffpatch and others use blank sprites when they add scripts that are not just for one sprite but set up or help control many sprites. One example would be a blank sprite that sets starting values for variables that are shared by all sprites - it doesn't really make sense to put it under any one of the sprites, so makes the project more organized. Another example would be a blank sprite that raises events that are used by many sprites. This can help to control the order that things happen in your project.

A blank sprite helps prevent lag when you are running in editor mode, as the editor doesn't need to keep highlighting the currently-running blocks.

If you go to editor mode its not lagghy