Many plant foods are inedible in their raw state due to the anti-nutrients that damage human physiological processes. Alkylrescorcinols, alpha-amylase inhitors, protease inhibitors, etc are all anti-nutrients that must be broken down by cooking before they can be eaten safely. Beans and legumes in general whilst rich in carbohydrate and protein, also contain protease inhibitors. The starch in cereals such as wheat, rice, barley, oats, and rye is also inedible in quantity unless cooked. Without being cooked it is less digestible by pancreatic amylase.
A vegan asked me last week if I would eat meat in its raw state, whilst I rarely do (I prefer to make life easier for my digestion in this modern world), the fact is I could, I have and I would. Meat, which can be digested in its raw state, where as vegetables are hard to digest and often toxic when eaten raw. Cereals become more digestible when fermented and cooked to neutralise the phytic acid and other toxic anti-nutrients.
Without this preparation we can often see a rise in conditions such as asthma, eczema.