It is often easier for the seller than having to worry about what the other sellers are doing, but it is often not so great for the customers. You know about competition from sports. Athletes and teams try to improve themselves to become winners. Winners themselves need to improve, as new challengers come up to test them. Weaknesses need to be reduced, strengths need to be made stronger.
Competition continually demands improvements.
The business world works similarly. Here, the areas of challenge are in pricing, quality, service and number of choices provided to customers. The best way to earn profits over a long period of time is usually by giving customers lots of choices, great service, high quality and low prices. Producers and sellers know that if they're not alert, their competitors will steal away a lot of customers and profits. Our American economic system is deeply rooted in competition, but other ways of doing business exist.