What is the first primary reason why feeding quokkas bread or crackers is prohibited?

Human food is detrimental as their digestive systems are designed only for native vegetation, potentially causing death

The prohibition against feeding quokkas is strongly rooted in their specific dietary requirements and the fragility of their specialized digestive tracts. Quokkas have evolved over millennia to process native vegetation, which includes specific fiber content, nutrients, and chemical compositions found in grasses, leaves, and bark. Introducing processed human food items such as bread or crackers severely disrupts this delicate system. These unsuitable foods can lead to severe illness, digestive distress, and ultimately, mortality, because the animal's system cannot properly process or extract necessary energy from these foreign substances.