Gusts take many 3-dimensional forms and, most inconveniently for pilots, don't stay put - plus you can't see them. In fact they could be characterised as 4-dimensional forms.
It's like whitewater canoeing with a blindfold and ear muffs.
You don't know what it is until you are in its teeth. Once you have been nibbled on by one of these beasts, your tolerance of the peanut gallery will be limited.