Capitalism rewards rare and valuable. Making something that customers value is important, but so is making something rare. Markets are competitive and initial success usually leads to other companies or new startups trying to copy and replicate such success for themselves. The last thing you want is for someone else to come along and capture your entire market for themselves.
It’s true that copying by competitors may or may not happen, and such copying by others may or may not be successful. But why leave that to chance? In fact, companies that are copying your business will likely use all their unfair advantages to crush you. If they have more funding, they can out-market you. If they have better engineers, they can develop a more stable product. If they have a brand name, they will use it.