As the Nintendo Entertainment System grew in popularity and entered millions of American homes, some small video rental shops began buying their own copies of NES games, and renting them out to customers for around the same price as a video cassette rental for a few days. Nintendo received no profit from the practice beyond the initial cost of their game, and unlike movie rentals, a newly released game could hit store shelves and be available for rent on the same day. Nintendo took steps to stop game rentals, but didn't take any formal legal action until Blockbuster Video began to make game rentals a large-scale service. Nintendo claimed that allowing customers to rent games would significantly hurt sales and drive up the cost of games. Nintendo lost the lawsuit, but did win on a claim of copyright infringement. Blockbuster was banned from including original, copyrighted instruction booklets with their rented games. In compliance with the ruling, Blockbuster produced their own short instructions—usually in the form of a small booklet, card, or label stuck on the back of the rental box—that explained the game's basic premise and controls. Video rental shops continued the practice of renting video games and still do today.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): According to Nintendo what was the danger in renting games?
would significantly hurt sales and drive up the cost of games