Reasons to need it range from your hand is shaky, your mouse/tablet drivers are incompatible at some level ( common lately even for Wacom), a subpar graphics tablet/mouse hardware issue, art program brush limits, and to whatever else. That is any line drawn in software and corrected, rather it be mouse or graphics tablet input. To finish off my current round of software reviews the last ones are for drawn line correction, stabilization, smoothing, tracking, altering, and other names given to the same task.
