You can survive indefinitely on nothing but beans and rice. You may not want to, however. I did live for an extended period where my food consisted mostly of beans and rice. I was grateful that I was able to eat as much as I wanted, of beans and rice, but I got very tired of it.
That experience taught me a lot about the importance of spices for giving some variety to a diet. It made a tremendous difference to be able to make the same food taste very different simply by adding some spices. I was also inspired to learn to grow fresh herbs for the same reason.
I was very sick during the first part of my beans and rice period. It was a relief in many ways when I became well enough to go outside and collect native plants to add even more variety to my diet.
Variety of taste is not the only reason to vary your diet. When you eat the same food all of the time, you are probably going to get some kind of malnutrition.
People who study nutrients and nutrition have discovered that different foods contain "phytonutrients". These are very small, or trace amounts of nutrients. Herbs and spices can supply phytonutrients.
An example of what phytonutrients can do is iodine. It is a small component of table salt. People who do not get enough iodine in their diets get goiters. These are swellings in the neck. They are caused by swelling of the thyroid gland.
Most people are in absolutely no danger of getting goiters because we eat many times more salt than we need. I don't know the numbers for other countries, but Americans average 30 times more salt per year than is necessary. Eating so much salt is causing other kinds of illness, including heart trouble, so we need to stop that.
I just mentioned iodine and table salt and goiters to give you an idea what a difference something in very small amounts can make to your health and your life. Phytonutrients can have an effect far out of proportion to their quantity.
Spice and herbs often have known medicinal value. They can be used to treat many kinds of illness. It is a good idea to investigate what some of these are when you make your selection of what to put in your preparedness supplies. They can even be part of your first aid kit.
Garlic is a strong antibiotic in addition to making food taste better. Garlic might be a good dual purpose choice for preparedness supplies.
Cinnamon is a spice that can reduce inflammation. Since strokes have been discovered to be partly caused by inflammation, use of cinnamon could be prevention for strokes. I like to put it on my breakfast cereal a lot for that reason. The same applies to nutmeg and turmeric. I don't like the taste of turmeric in oats, so I reserve that for main dishes.
Herbs and spices could be a very useful addition to your preparedness supplies, if you take a little time to learn enough to select the ones you need and like.