They do. You can buy the same ingredients and equipment at home and make it yourself.

When you buy coffee from Starbucks or whoever you are also paying for

1. Someone to make it for you.
2. Somewhere for them to work and possibly somewhere warm for you to sit whilst you drink it.
3. Someone to have purchased the equipment that you would otherwise have to buy up front.

Coffee shops also have to be located in high footfall locations where rent is going to be higher than your kitchen. Almost all of the cost to the retailer in providing you with the cup of coffee is the cost of providing the convenience rather than the product. But convenience still costs them money.