Creating walk cycles is one of the earliest skills for a character animator to practice. It will be a lifelong concern to create individuality to the walk.
The floursack is an exercise intended to instill a feeling for moving volumes rather than simply creating a series of two dimensional line drawings. The expression through body language of character and emotion without face or hand is emphasized.
Animation software often allows, or is even primarily intended for animation through the vehicle of designed and constructed digital "puppets". As with 3D animation, such 2D techniques allow animators who may be less skilled draftsmen nonetheless to create entertaining performances.
But mostly animation can simply be great fun rather than about technique.
Although, sometimes the techniques can be simple - but effective!