Why Startups Have to Innovate?

Why do startups have to innovate? Why do growth techniques work only once for a given product or service in a given market? Why is there no skill called “business”?

The answer is ==Anna Karenina principle==. Tolstoy opens Anna Karenina by observing: “All happy families are alike; each unhappy family is unhappy in its own way.” Business is the opposite. ==All happy companies are different: each one earns a monopoly by solving a unique problem. All failed companies are the same: they failed to escape competition.==

If a startup does not innovate but copy a product or service from the market leader, and the startup is targeting the same market, then people will not buy it because people are probably customers of the market leader already. Why do people buy the same thing for twice if their needs are fulfilled already?