It is important to understand the purpose of the copyright law and why the law grants copyright holders exclusive rights to their works for a period of time. Copyright law is intended to strike a balance. On one hand, it gives creators substantial control over the use of their works, so that they have an economic incentive to keep creating them. This benefits society by encouraging the creation of expressive works, which may contain facts and ideas (elements that are not protected by copyright) that people can use freely to expand knowledge within society.
On the other hand, copyright law limits the term of copyright and grants some rights to use works without the copyright holder's permission. This further promotes the flow of information and creativity in society.
Some people may not care about making money from their works and are happy to donate them to the public domain however, most expect to be compensated for using their time, talent, and creative energy. Even if music labels take a sizable amount of the money from sales of a musicians work, the musician will still make less money if sales are lost to illegal file sharing. Moreover, the labels use money from music sales to promote and support new or less popular musicians, labels may be less willing to do so if funds from music sales decrease due to illegal file sharing.
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