Drawing everything with the Freehand Brush Tool can lead to great results. There are times, though, when using drawing aids can help you achieve difficult effects. Using an assistant is not cheating. Creating artwork fast is a trait that is important in commercial work. Assistants free you from worrying about creating perfect shapes like circles and squares. This is especially true in mechanical drawings.
Different assistants in Krita have different purposes. Some assistants, like the mirror mode, help your eyes stay fresh to catch errors. Other assistants, such as the Multibrush Tool and mirror mode, help you focus on automating mirroring functions. The important thing with drawing aids is knowing when they are useful. Some assistants are a simple button, while others need to be managed.