Why does the law require people to obtain permission and pay fees for photocopying?

Copyright exists to foster the creation of all forms of intellectual property, including books. The copyright law gives creators of intellectual property a reasonable opportunity to be rewarded for their creative work. To the extent that copyrighted works are unlawfully copied; authors and publishers are deprived of their lawful income. This could reduce the incentive to write and publish books and, in the long run, harm education because investments of time and money in new books will not be made if others copy such books without compensation to the copyright owners.