Copyright imposes costs and burdens on the public, like any other government project. The benefit may not be worth the price. Government fills many important functions, but few would say that any one of these functions should be expanded to maximize output. For example, governments build roads, and this is very useful. But few leaders would advocate building every road that could be built.
Road construction is expensive, and citizens have other uses for their money.
Too much concentration on building roads means that other social and individual needs will be unmet. The same considerations apply to individual decisions. By spending more money, you can buy a bigger and fancier house. Most people would prefer the more expensive house, all else being equal. But given finite resources, at some point spending more on a house becomes a poor allocation of them.