Why are we normally advised to take bland and nourishing food?

Question: Why are we normally advised to take bland and nourishing food?

In the state of sickness our body function is the disturbed. That's why the digestive system also weekend and unable to to digest heavy foods. So, due to less effectiveness of digestion system we are advised to take bland and nourishing food that can be easily digested and  less energy is used in the digestion of food. we don't feel state of low energy.