Because we have a capitalistic economy, business is the main component of it. Business is in every corner of every sector of the market. Most everything you can possible think of that relates to the economy is business. Retail, services, agriculture, manufacturing, health care, even political campaigning all involves business. Even when civilizations were based on an agricultural type of economy, business transactions occurred.
Without business, humans would have to completely fend for themselves for absolutely everything. We would have to find our own food every single day. We would have to gather materials to create shelter because there would be no store to buy them and no real estate agent to sell a house. We would have to make our own clothes out of fabrics we weaved from raw materials we harvested. This type of society would not be practical at all. This is why people create trade with each other. Instead of having to provide ourselves with everything, we can focus on producing one product or expertise. We can then specialize in that product or expertise to make it the best on the market and then sell it for a profit. If everyone else does the same (in theory) we can all trade with each other and all obtain the best goods and the best knowledge.